Talk:IC 1101

Comments
It might be nice to get a picture of it on here, there are plenty floating around...

124.171.148.18 (talk) 08:49, 14 August 2010 (UTC)

Cause of size
"IC 1101 owes its size to many collisions of much smaller galaxies about the size of the Milky Way and Andromeda galaxies."

I thought that merging galaxies resulted in a smaller-sized galaxy. Am I wrong? -Theanphibian (talk • contribs) 02:35, 14 January 2011 (UTC)

No, but you aren't right either. What astronomers think of as "a pair of merging galaxies" is actually a moment (cosmologically speaking) of a Galaxy creation. Parent Galaxy gives birth to another one. Because they cannot emerge into existence from nothing at all, obviously (new galaxies, I mean)! Shee-un (talk) 19:25, 30 January 2011 (UTC)


 * I was thinking a bit differently. I was thinking about comparing the size of a galaxy to the size of its parent galaxies before they merged.  I had thought that a galaxy merger (creation of a new galaxy) results in the new galaxy being smaller in diameter than the parents (if the parents are of similar size).  I now realize that someone may also think "size" refers to the mass, in which case the new galaxy is almost exactly the mass of the parent galaxies summed together.  Saying that IC 1101 was created by smaller parent galaxies may be trivial correct in the sense that size refers to mass.  It may also be larger in the sense of volume or diameter, but I could not say. -Theanphibian (talk • contribs) 19:03, 21 February 2011 (UTC)

113.2 billion light years away?
I rather thought ~ 1 billion light years... --Gereon K. (talk) 09:18, 12 April 2012 (UTC)

Largest galaxy ever?
NGC 6251 in Ursa Minor is 3 Mpc (9 million light-years across), much larger than IC 1101. I've changed it. ==Johndric Valdez (talk) 05:46, 18 December 2013 (UTC)==

Let me restate this more strongly. NGC 6251 is a radio galaxy with a diameter of 9 million light-years, larger than IC 1101's 5.6 million light-year diameter record. This galaxy is immensely huge, 90 times the diameter of the Milky Way. So I think this galaxy has a better claim to the throne as largest galaxy than IC 1101. ==Johndric Valdez (talk) 05:51, 18 December 2013 (UTC)==


 * I don't know where you got that size for NGC 6251 from, but it's quite incorrect. I've blanked the size section of NGC 6251: see my comment on your talk page for more. - Parejkoj (talk) 04:53, 13 February 2014 (UTC)

Citogenesis example here?
I think we have a good example of Citogenesis here: per the literature (Uson, Bough & Kuhn 1991), the diffuse light radius of IC 1101 is somewhere around 500kpc (~300" measured radius, 320Mpc modern distance), which is maybe ~1.5 Mly if we're feeling generous. But there are hundreds (thousands?) of articles across the web quoting the 6 million light year figure. Could some other wikipedia sleuth figure out where this number originally came from?

We should correct this article, and the dozen or so other wiki pages that reference and quote the erroneous number. Not much we can do about the rest of the web, though... - Parejkoj (talk) 04:53, 13 February 2014 (UTC)


 * I've not looked into the sources in detail, but NED gives the major diameter as 1.2 arcmin, citing a paper from 1991 so way before Citogenesis is a concern. At a Hubble flow distance of 320 Mpc, that corresponds to about 110 kpc. Of course it's a matter of semantics to define a line between the edge of a galaxy and the intracluster light, but that does seem way out. Maybe someone confused the visible galaxy with the cluster x-ray emission? Modest Genius talk 17:56, 13 February 2014 (UTC)


 * Moderately recent paper stating 600kpc:

http://iopscience.iop.org/0004-637X/616/1/178 Lithopsian (talk) 22:26, 13 February 2014 (UTC)
 * Which cites that claim to which claims to measure a de Vaucouleurs profile to about 200 arcsec radius, which they equate to d=475 h-1 kpc. That does work out as about 600kpc, but even the authors only claim this as 'possibly' the largest galaxy then known. Still, that's an original and reliable source at least! Modest Genius talk 00:48, 14 February 2014 (UTC)


 * After some searching, I think I can summarize the situation as something like this: In 1990, Uson, Bough, and Kuhn published a short article in Science, the abstract of which says, "... the faint halo of this giant can be traced out to a distance of more than 1 megaparsec", which works out to a diameter of ~ 6 Mly. This was picked up by the media; e.g., the 1990 NY Times article in the External Links section, which report the size as "six million light years". The more detailed follow-up paper by the same authors in 1991 (Uson, Bough & Kuhn 1991) seems to walk the claim back a little. They give 260 arcsec as the *minor-axis* limit; since they say the galaxy has an axis ratio of 2, that means a semi-major axis of 520 arcsec. The "d=475 h-1 kpc" claim in the abstract of that paper [actually 425 h-1 kpc] is for the *mean* radius: (a b)1/2, which would be ~ 370 arcsec. So, depending on whether you want to use the mean radius or the semi-major axis, you get radial sizes of ~ 530 or 740 kpc, and diameters of 3.5 or 4.8 Mly. Peter Erwin (talk) 10:23, 12 December 2014 (UTC)

Size of the galaxy
So my edition was undone because apparently it is not 5.5Mly in diameter and we don't know the size of this galaxy. So all that "largest known galaxy" thing is a rumor? Is all the internet wrong?

I'm kinda confused now. Rough estimates are acceptablespace enth (talk) 00:56, 12 December 2014 (UTC)


 * See the talk section just above this one. In this case, "the internet" is certainly wrong, and by quite a large margin. We do know the size of it though: around 110 kpc (~360 kly), using the standard definition of size (major diameter of the obvious extent of visible light). Being generous, one could use the diffuse intracluster light for the size, but that's not at all a typical choice for the dimensions of a galaxy. Even going with that rather odd choice, it's no bigger than 1.5Mly in diameter. - Parejkoj (talk) 01:14, 12 December 2014 (UTC)


 * Ok. Well, I saw in your userpage that you have a posdoc in astronomy, so you probably know what you're talking about. Anyway, if you don't mind I want to ask you two things. First, care to supply a reference to that information of the size? Or did you calculate that yourself? I find it very unlikely that the entire internet is wrong. Second, why did you undo previous editions rather than putting that value in the article? Thanks PM ME URANUS (talk) 02:24, 12 December 2014 (UTC)


 * As I said, see the conversation immediately above this. Basically, either take the major axis size and distance from NED (which are also listed in the sidebar of this article) and convert via θ≈l/d to get ~110 kpc, or take the maximal extent of the measured visible light de Vaucouleurs profile of ~300" from Uson, Bough & Kuhn (1991) and the distance to get ~500kpc. In this case, "the entire internet" really is wrong. We could discuss both of those values in this article, but without context the first one, though large, isn't outrageously large, and the second needs quite a bit of elaboration to make sense to a typical reader. - Parejkoj (talk) 06:42, 12 December 2014 (UTC)


 * In my comment in the previous talk section, I noted that the Uson et al. (1991) paper gives you about 530 kpc for the mean radius, and about 740 kpc for the major-axis radius; the latter value translates to ~ 4.8 Mly for the (major-axis) diameter. (But since few giant galaxies have been analyzed in a similar fashion, the "largest known galaxy" claim is a bit dubious.) — Peter Erwin (talk) 10:34, 12 December 2014 (UTC)
 * So, if we cite the 1991 paper, can we use "1.06 - 1.48 Mpc" as diameter for the article, or would this be considered original research? Something authoritative needs to go into the article, else this issue will simply keep coming up again and again since even respected resources are republishing this misinterpreted data. — Huntster (t @ c) 22:07, 21 December 2014 (UTC)
 * (Pinging and  in case they don't have this page watchlisted. — Huntster (t @ c) 19:11, 22 December 2014 (UTC))
 * im also confused User:Hamterous1 (discuss anything!🐹✈️) 12:07, 18 April 2024 (UTC)

==

THIS SOLVES THE PROBLEM

The diameter of IC 1101 is 860,000 pc or about 860000*3.262=2.8 Mly See the wiki page [| Largest Known Galaxies]
 * According to NED at http://ned.ipac.caltech.edu/forms/byname.html, radial velocity is 23368±26 km/s, making this 1554 parsec per arcsec. If the galaxy is 90×35 arcsec, the maximum size is 1554×90 or 139.860kpc or 456,000ly (0.46Mly.). BY 1554*35 or 54,390pc or 177,000ly (0.17Mly). I.e. 140×54kpc.


 * Therefore, 5.5 Mly is improbable if not impossible.


 * Note; Is suggest they wrongly assumed the size was probably in arcmin not arcsec, which would give ~5.5Mpc.


 * Largest spiral galaxy I know, as stated in the literature, is NGC 6872 in Pavo, being 160kpc., (each arm spans an enormous 80 kpc.), so it very easily dwarfs our Milky Way’s mere 16±1.5 kpc size by a factor of five!


 * See article entitled “NASA’s GALEX Reveals the Largest-Known Spiral Galaxy” http://www.nasa.gov/mission_pages/galex/galex20130110.html, stating; "The spiral is 522,000 light-years across from the tip of one outstretched arm to the tip of the other, which makes it about 5 times the size of our home galaxy, the Milky Way."


 * This is therefore already bigger then IC 1101 too! Arianewiki1 (talk) 21:46, 28 December 2014 (UTC)


 * Sorry, but you cited another unsourced Wiki page in your first sentence stating 2.8 Mly, then you suggest it is <0.5 Mly, then a third sentence which is unintelligible. I honestly can't follow your maths. — Huntster (t @ c) 22:22, 28 December 2014 (UTC)


 * Smart guy, eh? I was answering a question posted by Tetra Quark on my User:Talk page, not you...


 * His question. "...tell me: Is IC 1101 really the largest galaxy? "


 * Just so you can understand.


 * 1) IC 1101 measures 90×35 arcsec according to NED
 * 2) Radial velocity is radial velocity is 23368±26 km/s
 * 3) Distance 320.5±22.4 Mpc
 * 4) At distance of 320.5±22.4 Mpc for a galaxy with apparent size of 90×35 arcsec, scale is 1554 parsecs per arcsec.
 * 5) Size (long axis) is therefore 1554×90 or 139.86kpc or 0.46Mly
 * 6) Size (short axis) is therefore 1554×35 or 54.39kpc or 0.17Mly
 * 7) IC 1101 is 139.86×54.39kpc. or 0.46×0.17Mly.


 * This is the dimensions of IC 1101.


 * [Reference is NED (as linked above), which has the data which you can easily verify yourself.]


 * However, NGC 6872 is 160kpc., meaning this is likely the biggest galaxy, as stated in the givenlink.


 * Tu capisci? Arianewiki1 (talk) 04:59, 29 December 2014 (UTC)


 * You never said who or what you were replying to, thus confusion. Thank you for clarifying. I wasn't intending to be rude, simply not understanding what you were aiming for. I have a lot of difficulty trusting some of the NED data points. As discussed above, several papers give a size for IC 1101 around 500 kpc to over 1 Mpc. Regarding NGC 6872, NED gives a major axis of 192.85 kpc, whereas the NASA article says 522 kly. NED says IC 4970 has a major axis of 42.86 kpc, which seems highly improbable to me. The NED distance measurements for NGC 6872 (using luminosity at least) says 62.5 Mpc, quite different from the 212 million light-years stated in the NASA article. I fully admit I'm no astrophysicist and could be misinterpreting the data, but discrepancies like this worry me. For IC 1101 at least, there seem to be a number of different figures based on what you're measuring, so it would be nice to get that sorted. — Huntster (t @ c) 05:46, 29 December 2014 (UTC)


 * "…I have a lot of difficulty trusting some of the NED data points." Wow. That's really bold. A novice judging experts...


 * Whether you agree with it or not, or even if it worries you, all results are properly referenced. Wikipedia couldn't give a toss if it right, wrong or irrelevant, just as long as the source is reputable and verifiable. (A NASA Site is reputable, regardless of your opinion. I.e. NASA/IPAC Extragalactic Database (NED). Do you have a more reliable reference, then?


 * IC 4970 is 22% the diameter of NGC 6872 —just look at the picture!!


 * (The size could include some the spray from the galaxy collision, not the size of the galaxy we see.)


 * Diameters also depend on the exposure or photographic colour sensitivity, and is therefore wavelength dependant. Galaxies look bigger or smaller depending on what and how it is imaged. Large errors are always quite problematic in astronomy. 42.86kpc appear on the blue plate. There are other measures. I.e. Diameter data point(s) for object IC 4970


 * As long as diameter estimates are comparable and reference, then quote that figure. Else specify a range.


 * I'd assume that the visual size should be 'standard', as quoted in some galaxy or deep-sky catalogue. Simply use the size in arcsec and use the Scale at Hubble Flow Distances (which is independent of observed size.) I.e. For IC 4970, 42×12 arcsec as stated in the "The Surface Photometry Catalogue of the ESO-Uppsala Galaxies" (1989) Arianewiki1 (talk) 07:08, 29 December 2014 (UTC)
 * Being suspicious of numbers quoted in NED for which you can't track back to the original source is entirely appropriate and wise. The fact that NED is a NASA database does not make it automatically reliable. NED is missing a named author, a date, and several other things a quality source will have. It's very useful, but it's just a database reporting information published elsewhere, and it doesn't always report it accurately. We are under no obligation at all to cite and trust a source we think is wrong, even if it meets all the definitions of reliable. —Alex (ASHill &#124; talk &#124; contribs) 04:05, 22 January 2015 (UTC)


 * Do you guys think that Universe Today is a reliable source? Because they claim that IC 1101 is the largest galaxy in the known universe. Also on another wikipedia page here claims that IC 1101 is the largest @ 2,800,000 ly in diameter. So until that page changes, IC 1101 is the largest hands down, so stop whining and complaining like kindergarteners that other galaxies are bigger and that IC 1101 is the largest isn't backed up (It is). PS People who think that NGC 6872 is the largest Galaxy didn't do their homework! NGC 6872 is dubbed the largest **SPIRAL**, not the largest galaxy, if it was the largest it would have been dubbed the largest galaxy. Also here is a quote from NASA about NGC 6872 "Measuring tip-to-tip across its two outsized spiral arms, NGC 6872 spans more than 522,000 light-years, making it more than five times the size of our Milky Way galaxy.". So no NGC 6872 is not the largest. Hopefully closing this debate once and for all - Davidbuddy9 (talk) 14:21, 7 February 2015 (UTC)

Concerning edit : Changed distance from megaparsecs Why?
@ Huntster. Please explain this earlier reversion of this edit of mine.

"…approximately 320 Megaparsecs, 320 Mpc from Earth." to "...approximately 320 Mpc from Earth. "

The standard unit of measure for galaxy distances in Megaparsecs, not Gigalightyears. I.e. Andromeda Galaxy (in kpc, as it is less than 1.0 Mpc.), Centaurus A: "Distance estimates to NGC 5128 established since the 1980s typically range between 3–5 Mpc." , etc.

Also the given NED reference in the table "Quantities Derived by Redshift for IC 1101", express the 'Hubble Flow Distance and Distance Modulus' as 320±22.4 Mpc., verifying this is the case. There is no evidence of gigalightyear used here at all, and even if it was, it not a recognised galaxy scale. (many sources) Hence 320 Mpc in the first instance is perfectly correct.

As said in Galaxy page Introduction; "The observable universe contains hundreds of billions (more than 1011) of galaxies. Most are 1,000 to 100,000 parsecs in diameter and usually separated by distances on the order of millions of parsecs (or megaparsecs)." confirms this. Another, "A distance of one million parsecs is commonly denoted by the megaparsec (Mpc). Astronomers typically express the distances between neighbouring galaxies and galaxy clusters in megaparsecs." 

Yes there are many galaxy pages that say things in terms of light-years and their units, but the 'standard' is Mpc for galaxies.

I would remind you if you make such edit changes, you should say what was changed. It helps track edits properly.

Look forward to your response in me not reverting this.

As to the rest of the edit, I completely agree with the changes you made.

(If I seem terse, it is because I dealing with too many would-be edit warriors, today. Sorry.)

Cheers.

Arianewiki1 (talk) 11:00, 21 January 2015 (UTC)


 * Yes, be calm, it was just an error on my part. I've fixed it. Sorry for the delay, I never received the ping from this. — Huntster (t @ c) 07:36, 24 January 2015 (UTC)


 * Actually, I have zero problem about this, and I thank you for the reedit. Don't understand the non-ping, but sometimes this happens (probably somehow an error of mine.) Either way, the figures give the correct distance, so changing them is not desperate. After sometime to think about this, I have likely been too aggressive here and on some of my earlier comments. I'll try to improve towards the edits from now on. Thanks. :) Arianewiki1 (talk) 11:37, 25 January 2015 (UTC)

Reference Quoted Figures
Hi Ashill

Could you please explain where you got the value "200,000 ± 40,000 (half-light radius)" from the reference. for the figures now quoted in the article. What units are they?

I've never seen this parameter associated with galaxies anywhere.

I can't see these figures taken in the article, where they calculated, as the sizes are in kpc.?

(I looked through the article twice. i don't see it )

There is new comments here by Primefac and me. at;
 * From the cited source, with calculations converting size in arcmin to ly in the comment. The units (ly) are in the table header (a silly place, in my opinion, but that's how it's defined in the galaxy infobox). Which parameter have you never seen? —Alex (ASHill &#124; talk &#124; contribs) 03:24, 22 January 2015 (UTC)
 * (The number is exactly the one in the comment you just pointed to; that's the reference I used.) —Alex (ASHill &#124; talk &#124; contribs) 03:28, 22 January 2015 (UTC)
 * I've added another bit to the text, citing Uson et al (1991) (as suggested above) and quoting them as saying IC 1101 is "possibly one of the largest and most luminous galaxies in the universe." (That's one of the last sentences of the peer-reviewed Astrophysical Journal follow-up paper, ie not the original Science paper or the popular media reporting on it.) —Alex (ASHill &#124; talk &#124; contribs) 04:00, 22 January 2015 (UTC)

Alex, absolutely excellent work. The calculation is important to know, so we can at least trace a source. Thanks. Arianewiki1 (talk) 04:46, 22 January 2015 (UTC)

Effective radius
The information in the Effective radius page is so out of date, words just fail me.

These papers on this were published around 1969. Whoever introduced this text here has absolutely zero idea of how or why effective radius means. The graphic regarding galaxies shown here is irrelevant, as is the Swinburne link.

The ideas behind this dates back to the idea of the theoretical estimating of mass distribution. It relies on finding a radius-magnitude relationship. The concept is to describe the mass density / density profile out to the edges of the galaxy, to the theoretical dark matter halo. Reff is represented in arcsec, and sometimes relies, in modern times, on tracers using globular or planetary nebulae. I.e NGC 5128 tracers is 300 arcsec / 6 arcmin, for example. The galaxy is 25.7×20.0 arcmin, or roughly five times larger. Hence, describing galaxies by there half-light diameters is just nuts. Worse is that you have to also know the surface brightness, calculated from the magnitude, then assume the distribution of the light, follows some general law (which has differing values based on some average, that is different between astronomical types), and somehow out pops some diameter.

Q. Do spiral galaxies have effective radii? (Why doesn't the article say so?)

Q. What is the distribution form of a density profile of an elliptical galaxy including the dark-matter halo?

In the end, why so complicated. For most uses, the diameter is based on the RC3, UGC or PGC galaxy catalogues gives diameters based on photographic emulsions. Knowing the magnitude limit, sets the galaxy size, which is based on the exposure time. This determines the apparent size of the galaxy. Knowing that, means you determine, from the distance, the true scale of the galaxy. Please forget this half-radius stuff on elliptical galaxies.

Effective radius is not easily related to the half-light radius, especially when its use is already dubious on elliptical galaxies. (as explained above.) I have reverted the edit until we have evidence to prove otherwise.

Q. What is wrong with quoting the 1973 UGC size here? Arianewiki1 (talk) 02:43, 23 January 2015 (UTC)


 * Please sign your message Tetra quark (don't be shy) 02:41, 23 January 2015 (UTC)


 * I would have, if it didn't get caught in the cross edits. Please slow down. It is not a race. It helps everyone. Arianewiki1 (talk) 02:44, 23 January 2015 (UTC)
 * The Fisher et al (1995) reference says, in the right column of page 540, "For a de Vaucouleurs r^{1/4} law, the effective radius is the radius within which one-half of the light is emitted." Now, they're compiling effective radii from the literature, and it's the mean of those published values compiled in the Fisher et al paper (excluding one factor of 2 outlier) that is now reported in the table on this article as the half-light radius. (Comments on the effective radius are probably best made on that article's talk page, not here -- confuses the issue.)
 * I think that, given the apparent misuse of this particular Wikipedia article around the interwebs, it's important that we be very clear about what we're talking about in terms of size. I think that's not clear in the UGC reference you're referring to (as it is in the NED database), which is why I think getting the number out of a primary or secondary source that allows us to explain what the measurement means is crucial. And for this particular, well-studied, galaxy, it's not too difficult either. —Alex (ASHill &#124; talk &#124; contribs) 03:02, 23 January 2015 (UTC)

If you want the formal explanation, and me to change the Effective radius, I'm happy to do so, but it is pretty hard work. My opinion is by good experience not guess work.

I left a question on this link above.

Q. What is the distribution form of a density profile of an elliptical galaxy including the dark-matter halo?

If you can answer that, it shows why this statement effective radius and half-light radius are disconnected. I..e Vaucouleurs r^{1/4} law, does not apply to elliptical galaxies here.

The matter density profile of elliptical is distributed rho=(a^2+ r^2)-1, with a being around 2.8 kpc, which is derived by observations. I.e. it is not r^{1/4} law.

Please show evidence that half-light radius = effective radius for ellipticals. I explained why?

Do you need more detail?

Arianewiki1 (talk) 03:09, 23 January 2015 (UTC)
 * The most-used definition of effective radius is the radius at which half the light is contained. For example, page 243 of Sparke & Gallagher's 2007 galaxies textbook. And that source (just like the Wikipedia page) uses effective radius only for roughly axisymmetric objects (ie elliptical galaxies or bulges of spirals, but not disks). Anyway, what's relevant for this article is that we state meaningful numbers that are in reliable sources, properly explained. I think we do a decent job of that now. —Alex (ASHill &#124; talk &#124; contribs) 03:40, 23 January 2015 (UTC)


 * @ASHill. Absolutely Great!! Now I can properly answer this issue. Yes, I do own this reference. However, this R^0.25 profile is for luminosity (or surface brightness) NOT physical size. It is based on B- band images, assumes midsized elliptical galaxies, and luminosities of elliptical brighter than 3 billion Sol. Size is on pg. 250-251, but those quoted in NED are from the maximum axis, where x=y=z in formula (6.5). Dimensions taken on plates are physically measures, based on a stated magnitude limit / minimum surface brightness. Around 20th magnitude. obtained from the plate itself. I.e. If I take a longer image, the dimensions will typically be larger, but so will on some magnitude limit/ surface brightness limit.  Usually even 20.0 V mag / B mag or 25.0 B-mag arcsec^-2^. Alternatively, it is Intermediate surface brightness or the Diameter used for calculating "total" magnitude.


 * Figure 6.9 (pg.252) also says "…Contours show probability density; the top contour level is for probability density 4.5 times higher than that at the lowest." This is where the comment in this discussion above on NGC 5128. where I said "NGC 5128 tracers is 300 arcsec / 6 arcmin, for example. The galaxy is 25.7×20.0 arcmin, or roughly five times larger." I.e. Half-light radius is not a good estimation of the effective radius.


 * However, IC1101 is an S0 galaxy, whose density profile is unlike Fig. 5.14 of NGC 7331, but highlight the point.


 * Where is the size cut off for NGC 7331 here? 9 arcmin (NED gives 10.5 ) which is from the POSS1 103a-O plate used in the UGC survey of 1973. The half-light radius is about 2.3 arcmin. (Roughly the RC3 result) I.e. About a fifth the effective radius of 10.5 arcmin.


 * Q. On the galaxy, NGC 7331 on the page is the apparent dimensions of 10.5×3.7 arcmin. Should the size be the half-light radius of 2.3 arcmin or the effective radius of 10.5 arcmin? Assuming the local group scale of 74 pc per arcsec, then do we use 10.2 or 46.6 kpc., for the major axis? Size is 46.6×16.4 kpc., if we adopt POSS1 103a-O plate, UGC survey (1973) as a method.


 * Look forward to your thoughts, as this applies to all quoted values for galaxies we use.


 * Important. The evidence shows effective radius does not equal half-light radius. Fisher method is an general approximation.


 * Hope this is clear enough. :) Arianewiki1 (talk) 05:24, 23 January 2015 (UTC)


 * Open Comment. I read you have studied the Milky Way and the ISM on your user page. It is interesting that the molecular hydrogen and cool dust is the M.Way is from 3 to 8 kpc, though the atomic hydrogen ranges between 3 to 25 kpc. (all from the galactic centre. The ratio is about 3:1 in distance, though for other galaxies it is between 3:1 to 5:1. Both these values ranges I seen several times in the literature. The drop off in luminosity is logically proportional, highlighting the complex arguments in which to use. By mass, the ratio between the HI and atomic Hydrogen are about equal at ~10^9 solar masses. Some theoretical 'half mass ratio' would be around 11 to 12 kpc.


 * For S0 galaxies masses are between 10^10 and 10^12 sol, and the large cD's 10^13 to 10^14, with diameters 10-100 kpc. and 300-1000 kpc., respectively. (Quoted from Padmanabhan "Theoretical Astrophysics. Vol 3, Galaxies and Cosmology", Cambridge University Press, pg.44 Table 1.2 "Galaxy Parameters - II" (2002). The size for IC 1110 is 63.4 kpc, which is seemingly too small for a cD galaxy let alone S0. Twice this is 126.8 kpc., three 254 kpc., five 321 kpc. My initial early calculation for IC 1101 was c.140pc. Here 63.4 kpc. for IC 1101 is a little small.


 * My open suggested solution to this appears in  Arianewiki1 (talk) 06:27, 23 January 2015 (UTC)


 * Another edit conflict. Ah! My reply it to the previous post . Try again. @ASHill


 * @ASHill Yes I read this quote. The use of this was because of the serious and limiting difficulties to find a realistic result. You are correct is some of the things you say, but in this case the simpler explanation are probably the best. These highly esoteric arguments, especially if this is towards describing towards elliptical galaxies. However, this explanation cannot be used with spirals or irregular, and especially quasars.
 * As Parejkoj says; "Being generous, one could use the diffuse intracluster light for the size, but that's not at all a typical choice for the dimensions of a galaxy."
 * This subject is not very simple to solve or prove, but is an awfully lot of effort for the size of an one object whose boundaries are already shrouded depending on some adopted method. I feel it is worthy to explore this further, but I think for the audience who reads this will be lost in utter confusion.
 * The results are meaningless without context, and if the context is already highly debatable, it means little. Sure add half-light radius = effective radius for all ellipticals and/or IC 1101, but it is misleading at best, and of little practical value. Considering astronomers efforts over just on 100 years of deep study, they still have yet to come up with a universal method of deciding a galaxy's size. Whist not an answer, it reflects the truth of the matter.
 * Your devotion to searching for a result for IC 1101 is honestly appreciated. It is better than nothing. Thanks.


 * Comment: My apologies for the missing tildes, again. In edit conflicts, I copy the text, open a new window, then paste it. However, it somehow removes the tildes. Frustrating. Arianewiki1 (talk) 04:11, 23 January 2015 (UTC)
 * It is unclear to me what any of this discussion has to do with the references or what we should say about IC 1101. All the sources we're using say that effective radius is simply a definition meaning half-light radius. The attempts here to say that it means something else (or nothing at all) strike me as original research, and irrelevant to reporting what the sources say even if it's not original research. And re your comment about this not being clearly related to the matter density profile: of course it doesn't; it's a half-light radius. —Alex (ASHill &#124; talk &#124; contribs) 13:41, 23 January 2015 (UTC)


 * @ Alex ASHill "The attempts here to say that it means something else (or nothing at all) strike me as original research." Yes it is original research if it appears in an article, but it is not within a discussion. I.e. You have yet to prove effective radii = half light radius. The decision here has consequences for EVERY galaxy article.


 * My suggested methodology was;


 * Criteria should be.
 * The diameter should be quoted from visual images. I.e. POSS1 103a-O or POSS2 103a-O
 * If no visual image is available, the diameter quoted should include the Plate colour info.
 * All diameters should be referenced to their source. I.e. RC3, PGC, UGC. (RC3 tell you the size in from a B-plate.
 * Other wavelengths beyond the visible should quote the size and source. I.e. 2MASS, which is applicable to under-luminous galaxies.
 * Else any size should be referenced to the source where it was taken. *
 * If size cannot be determined, the example calculation for IC 1101, which is simple to understand, should be used.


 * Considering all the errors involved, quoted sizes are mostly 20% to 40% in error. Most quoted results are rather poorly known, anyway.


 * If you really want to be pedantic, we could use T. Padmanabhan's "Theoretical Astrophysics. Vol 3, Galaxies and Cosmology", Cambridge University Press, (2002). However, explaining dimensional reductions here, is beyond our scope.


 * Let's be clear. This whole issue was started here.


 * My central response here is to the request by Huntster "My first thought would be to use the NED data, but given the tremendous disparity between different reports, I think this needs a degree of consensus from the community. I'd appreciate any and all thoughts so as to put this to rest." and Tetra quark "That really is a problem" This is what we are trying to find out.


 * Secondly, I still see little evidence the effective radii = half light radius. Tetra quark last edit, which I reverted, and you changed back again, links these pages together. Evidence says the contrary, as I have already proved in the text above. Unless you can show effective radii = half-light radii, it should be reverted. Else, create a new page on half-light radius explaining it.


 * Lastly, the values quote in the article are in light years, whereas the reference results are in kpc. Converting it to light years, which is a non-standard unit. If used it should be as per the reference.


 * Comment: NED is a primary source of data, just as SIMBAD is. If the argument that NED isn't, then all references to SIMBAD or also the case, changing +1000 pages of Wikipedia articles.


 * The reason the adoption of the current value is because it appears in a verifiable reference, even if its interpretation is questionable. Arianewiki1 (talk) 00:33, 24 January 2015 (UTC)
 * Every source cited here says that effective radius = half light radius. If you want another, I checked Binney & Tremaine's Galactic Dynamics textbook (p. 21 of the 1987 edition): "the effective radius R_e is the radius of the isophote containing half of the total luminosity" (emphasis in original). How clear can it possibly be? I see nothing at all questionable about the interpretation of the current source, other than that there are a wide variety of ways to define the size of a galaxy, making it particularly important to choose sources that explain their measurement and reasonably-completely report what the source says.
 * I don't see what the decision here has to do with other galaxy articles: this galaxy's circumstances are fairly unusual.
 * Simple multiplicative unit conversions (eg between pc and ly) are absolutely something we can do without citing a source, unless you or another editor challenges the validity of the conversion; I'm pretty sure that's not happening here. —Alex (ASHill &#124; talk &#124; contribs) 02:26, 24 January 2015 (UTC)


 * Umm. There is so much difficulty here in the usage of these terms. I'm sure I could cheery pick other sources that could counter this. Treating elliptical galaxies as if they are distributed like globular star clusters is fraught with difficulties. I too have this book, but you have misquoted. If you read the footnote, same page, it says "The effective radius is measured on the plane of the sky, and is not to be confused with the half-light or median radius, the radius of the sphere containing half the luminosity." Does this mean these are equivalent? "Every source cited here says that effective radius = half light radius." No. That is doubtful, and I've explained it in all the text above. Luminosity does not equal surface brightness, magnitudes, nor or isophotes. (It is related, but not equivalent.)
 * NED specifically says; "Effective Radius : The distance from the center of a galaxy within which half of the total luminosity is included (cf. Holmberg radius).", which comes from the "Glossary of Astronomy and Astrophysics", J. Hopkins, University of Chicago Press (1976) [Half-light radius is nor mentioned, but that's trivial, but is an observation of its importance.] 'Holmberg radius' is mentioned in German Wikipedia, but not in English. It is defined in 1958 as the radius of a galaxy out to an isophote, representing a blue magnitude of 26.5 per square arc second. A sample of how rotation curves have replaced this is at NED (If you want an historical outline of the subject, read the next few pages, which is from the Annu. Rev. Astron. Astrophys (1979)
 * de Vaucouleurs r^0.25 law written in 1948 was based in the times when galaxy imaging was still poor. As this points out (the Sersic index), has a variance between 6 and 2. If IC 1101 is very luminous, then de Vaucouleurs r^0.25 (1948) is likely invalid. As pointed out, B magnitudes are not very good indicators of sizes for elliptical, for obvious reasons. In the NED (1979) article it says; "In fact, there seem to be significant departures from de Vaucouleur's law in the outer profiles of elliptical galaxies which correlate with environment. Furthermore, the total light in the envelopes of some cD ellipticals shows no sign of converging to a finite value,, making the determination of Re operationally impossible. Finally, if ellipticals contain appreciable amounts of dark material which is more extended than the luminous material, Re as determined for the stars alone may have no connection with the true mass distribution of the galaxy." (Precisely as I've already said!)
 * As I pointed out to you before, the best way of expressing elliptical galaxy radii is in term of the half-mass radius, which is greatly constrained because of the maximum rotational velocity of the stars. I.e. The Wilkinson & Evans (1999) (quoted on pg.17), then later, in this book. Globulars and planetary nebulae, have been useful indicators here. (Of course, IC 1101 is far away, so there has to be more assumptions here.)
 * You should know, in the past few days, I have been in contact with some associates on this being half-light radius a way of estimating galaxy sizes. They basically agree with this method dubious at best, especially in the availability of more recent data. It simply assumes the drop-off in light is exponential from core outwards - it is not nor that simple. It may work for an average elliptical galaxy, but the variance between the make the result doubtful. There are frankly better and more reliable methods to determine radius of galaxies. Your statement, which I referenced to them, and one somehow already knew, was your statement; "Being suspicious of numbers quoted in NED for which you can't track back to the original source is entirely appropriate and wise. The fact that NED is a NASA database does not make it automatically reliable. NED is missing a named author, a date, and several other things a quality source will have. It's very useful, but it's just a database reporting information published elsewhere, and it doesn't always report it accurately. We are under no obligation at all to cite and trust a source we think is wrong, even if it meets all the definitions of reliable." This was thought to be a little unfair, as it is 'collect point' as a steeping stone to deeper investigation. It was directly pointed out to me, if NED wasn't a good resource, then pray-tell where else do you go? You CAN track back the source in NED, with the ADS in "Journal Abstracts." (They were not written out in full to avoid overcrowding the webpage.) DIameters, as they point out, appear accessible from the 'Diameters' section of the main page. NED is also useful for batch jobs on galaxy data, being frequently used for professional papers. If you have any issues, they happily receive your feedback.
 * As for units here, they should be in kpc or Mpc, not light years (or their variants.) Changing thing into light years is annoying, because you have to convert them back in parsecs to do the calculations. Beside most sources quote units of parsecs, which the media coverts in light years in the expectation that other 'understand this better. Frankly, the source units must be quote, and any 'conversion' must follow, else we think this is the 'primary' data. (It is also susceptible to miscalculation, and often will confused as source data.)
 * Alex, you are clearly well versed to discuss this topic, and it would certainly benefit from an independent third umpire. Our discussion has greatly helped me be more appreciative of the issues involved here, guiding me to a wider viewpoint. To the average reader this is fairly esoteric, and is well beyond most people's comprehension.
 * Although have do still reservations of your position here, at least the conversation has been mostly cordial and productive. Cheers. :) Arianewiki1 (talk) 15:25, 25 January 2015 (UTC)
 * I double-checked my Binney & Tremaine (1987 edition): there is no such footnote, and I verified that my quotation does not miss any context. The footnote you mention is in the Second Edition, which I just looked at now. However, the footnote refers to the half-light radius on page 17, but page 17 actually only mentions the half-mass radius. If your statement is that the "half-light radius" actually has some other meaning than "the radius which contains half the light", that was a subtlety I wasn't aware of. But I'm not so sure that the references support that definition.
 * You suggested a difference between the half-light radius and the half-luminosity radius, but luminosity and light (ie flux) are directly proportional (by definition: luminosity = flux * distance^2), so those radii are the same for a given galaxy.
 * Of course this is all dubious, and the "size" of a galaxy is an idea with limited utility and lots of caveats. But this is a number to quote in an encyclopedia. When a layperson asks "what is the size of a galaxy", I think this is as good a number as we can reasonably provide. I definitely think that a number directly tied to the light is better than a number which -- though more physical -- requires some interpretation like some parameterization of the distribution of mass. Though of course including a description of the distribution of mass in addition would absolutely be good.
 * I feel like this discussion has veered way into minutia. Apologies for the extent to which I've dragged it there. I know there are others reading this thread, and they're of course welcome to chime in. But I'm not sure there's a real disagreement to settle here other than whether half-light radius = effective radius. I think it pretty clearly does, but if you want to change the terminology in the article to remove the mention of "half-light radius" and say "the radius which contains half the light", I wouldn't object. —Alex (ASHill &#124; talk &#124; contribs) 15:10, 26 January 2015 (UTC)
 * As an alternative to the more visible "half-light radius" tag, a more detailed explanation for the figure could be enclosed as a note, similar to how references are formatted. If wording can be agreed upon, I can stick it in the infobox. — Huntster (t @ c) 21:31, 26 January 2015 (UTC)

Size
IC 1101 has a mass of 100,000,000 suns, which is 1000 times more than the milky way, yet it's supposed to be half the size of our galaxy(almost).--I am. furhan. (talk) 18:59, 24 January 2015 (UTC)i am. furhan.
 * Huh? It's much larger than the Milky Way in size (no matter how measured) as well as mass. —Alex (ASHill &#124; talk &#124; contribs) 20:01, 24 January 2015 (UTC)


 * @I am. furhan. IC 1101 is 64±12 kpc, extending 600 kpc., and the Milky Way 31–37 kpc. It is much bigger, with an estimate 1014 stars, averaging an estimate 0.8 M☉. With gas and dust, and even dark matter, the mass is c. 1016M☉. Mass of the Milky Way 0.8–1.5×1012 or 1,000,000,000,000 suns
 * Hence is is more likely 10,000 times bigger by mass, five times the size, 6× volume at 64 kpc and 5000× at 600pc.(and that assumes the Milky Way is spherical, not as a flat disk where most of the stars lie.)
 * IC 1101 is a plainly a very huge galaxy. Arianewiki1 (talk) 16:33, 25 January 2015 (UTC)

Possible New Data to Drop
I found this recent data on the net from the SDSS7 survey on ViZier, that could be useful.

"Parameters of spiral galaxies from SDSS7", by Hall, et al. (2012). This release gives the i-band parameters (Table 1), which is readily found in ViZieR. .

This quotes in the table, masses, velocities and radii. (You might have to add the object IC 1101 in the first field.)

Oddly, this is in with a bunch of spirals, which I don't understand.

I's add it but someone might revert it. ;) Arianewiki1 (talk) 04:55, 26 January 2015 (UTC)

List of largest galaxies
A recent edit copied character-for-character the list from list of largest known galaxies. I see no reason why that list needs to be duplicated here, so I've removed it (now twice). I'll also incorporate a link to the list into the text. (There are also issues with the list pertaining to the different and subjective definitions of "size" of a galaxy, but that's a topic in relation to this list that belongs at Talk:List of largest known galaxies.) —Alex (ASHill &#124; talk &#124; contribs) 14:37, 4 March 2015 (UTC)


 * Agreed, there's no reason for such (bulky) duplication of effort when a link to that article will suffice. — Huntster (t @ c) 16:26, 4 March 2015 (UTC)

Scientific notation and the kilolight
I agree that it is best to avoid use of scientific notation in prose. The problem arises from the use of the Convert template with non-existent units involving the kilolight, megalight and gigalight. There is no such thing as a kilolight and therefore also no kilolight-year. A possible compromise is a light-kiloyear but I prefer to avoid the issue and write out as thousands of light-years. Dondervogel 2 (talk) 19:18, 12 April 2015 (UTC)
 * I think that scientific notation is preferable to making up units like the kly or Gly (even though I have seen at least one textbook that uses those units); "thousand lightyears" or "billion lightyears" is also OK. But really, the standard units kpc, Mpc, and Gpc are just fine for distances that large; it's not like readers are likely to have a clear conception of what one million lightyears means anyway. However, "lightyear" or "light-year" is the unit, so if we were to attach an SI prefix to it, it would be kilolightyear or kilolight-year. —Alex (Ashill &#124; talk &#124; contribs) 14:03, 13 April 2015 (UTC)
 * The issue affects many other articles, so is worth thinking through carefully. The problem is caused IMHO by the Convert template which encourages proliferation on Wikipedia of the units kly, Mly and Gly beyond all proportion of their adoption outside WP.  At the moment this article has parsecs leading (with appropriate SI prefix kpc, Mpc or Gpc) with the number of thousands, millions or billions of light-years in brackets.  I think this works well. Dondervogel 2 (talk) 14:20, 13 April 2015 (UTC)
 * I agree on all counts. —Alex (Ashill &#124; talk &#124; contribs) 14:23, 13 April 2015 (UTC)
 * Great. I left a note at WP:Astronomy to see what others think. Dondervogel 2 (talk) 14:26, 13 April 2015 (UTC)
 * "Kilolight-year" = "kilo(light-year)", not "(kilolight-year)", and is 1000 light-years (and you know it). There is no actual problem with it, and anyone familiar SI prefixes and the abbreviation for the light-year, will understand things like "Mly". Whether it should be used depends on the context, IMO. I'd say that if spelling it out makes it tedious to read (for example because many values are mentioned), then don't spell it out. As for ly vs. pc, it is best to present both. If I read something in only parsecs, I always ask myself how many light-years that is, so that I can compare it to sizes I know, such as the diameter of the Milky Way and the distance to Andromeda. --JorisvS (talk) 15:11, 13 April 2015 (UTC)
 * Sure I understood what was intended - otherwise I would not have been able to fix it. The issue is whether Wikipedia should be in the business of inventing or promoting neologisms when there's a perfectly good alternative.  Dondervogel 2 (talk) 16:23, 13 April 2015 (UTC)
 * What's the perfectly good alternative? And how is using SI prefixes and normal abbreviations a neologism? --JorisvS (talk) 17:26, 13 April 2015 (UTC)
 * The perfectly good alternative is "30 thousand light years" instead of "30 kly". The neologism is that kly is hardly ever used outside WP (in contrast with kpc which is common).  For example this search for kPc, Mpc, Gpc and parsec yields more than 300 scientific publications, increasing to more than 50,000 hits for this search for kPc, Mpc.  By comparison, it's hard to find any hits at all from similar searches for kly, Mly, Gly and light-year.  Try it, and you'll see what I mean.   Dondervogel 2 (talk) 18:47, 13 April 2015 (UTC)
 * That's not quite a fair comparison; the academic literature (which you're searching) doesn't use light years much at all either. (Though ly is very difficult to search for, since it appears all the time.) The relevant comparison is really to popular science books, perhaps intro-level astronomy textbooks, and the like that aren't terrified of numbers (like news reports generally are) but are intended for a general audience (unlike scholarly articles), since that's more representative of the target audience (I think) of Wikipedia's astronomy articles. But I agree that kly, etc are very uncommon; I know of only one source that uses them (Zeilik's Astronomy: The Evolving Universe general-audience textbook). Even that textbook includes "light year", "parsec", "kiloparsec", and "megaparsec" but not "kilolightyear" or "megalightyear" in its glossary. And the same author uses pc, kpc, Mpc, etc exclusively in his textbook intended for astronomy majors. But getting into comparing to sources on what is fundamentally a style choice is not a rabbit hole I'm eager to open based on recent experience, to say the least. —Alex (Ashill &#124; talk &#124; contribs) 19:20, 13 April 2015 (UTC)


 * I don't oppose, in general, writing "30 thousand light years". I do think that we should switch to abbreviations when it otherwise becomes very tedious reading because there are too many "thousand light years"s or the like in there (I know, it's subjective, but as a rule of thumb), when used alongside (other) abbreviated units, and in infoboxes and the like. And when abbreviations are used I think it is a service to our readers to include the value in light-years alongside its parsec value. --JorisvS (talk) 08:29, 14 April 2015 (UTC)

Note: This problem has already been discussed:

Wikipedia talk:WikiProject Astronomy/Archive 17

SkyFlubbler (talk) 12:13, 15 April 2015 (UTC)


 * Funny that. My recollection of that discussion was that it was mainly about whether to use ly or l.y., but you're quite right - the heading was clearly about use of SI prefixes.  They are very rare, never needed, and therefore should not be used.  As you can see the problem has not gone away, and the present discussion arose because an edit of mine replacing 'kly' with 'e3ly' was reverted in order to avoid scientific notation in prose.  I understand that point, which is why I am seeking a solution to the endemic problems caused by Convert. Dondervogel 2 (talk) 17:53, 15 April 2015 (UTC)

Lead image
An editor has pointed out that the lead image (File:IC 1101, telescope image.jpg) is an artist's impression. It certainly looks prettier than any of the real images of this galaxy, but would a real image be better for the lead? —Alex (Ashill &#124; talk &#124; contribs) 13:51, 10 May 2015 (UTC)
 * In my opinion its better to have an artist's impression rather than having nothing. We can decide what looks better only if he/she has a properly licensed, real image(telescopic image) to offer.-- Chamith  (talk)  14:36, 10 May 2015 (UTC)
 * If you have a specific real image in mind, post it here and we can discuss which is better. I've not seen any such image that was at all useful. — Huntster (t @ c) 16:00, 10 May 2015 (UTC)
 * What about this one, which I believe was used in this article until it was removed as a copyright violation? ko:파일:IC 1101 dss2.jpg We'd be using it based on fair use, for which the argument is exactly as strong for the current artist's impression as this image.
 * My particular objection to the artist's impression is that, because we don't have the original source, we have no description of what it represents and which choices made in creating the image were scientific and which artistic. —Alex (Ashill &#124; talk &#124; contribs) 23:52, 10 May 2015 (UTC)
 * As the image was removed due to copyright violation I cant firmly decide whats best for this article. However as you might have already noticed we use artists impression to represent many astronomical objects that can't be clearly seen through telescopes. For example article Black hole uses various artist impressions/computer renditions to depict how a black hole may actually looks like. However I would like to know what you meant when you said that we don't have any description of what it represents. Aren't there any solid proof to say that this represents IC 1101? Source says it is an artist's impression of IC 1101. Well if you think that's incorrect then indeed it shouldn't be used in this article for the sake of factual accuracy -- Chamith   (talk)  04:30, 11 May 2015 (UTC)
 * Quite the contrary, I think its better to use this image as its much more reliable than an artist's impression. Just my opinion-- Chamith  (talk)  04:37, 11 May 2015 (UTC)
 * We certainly do use artist's impressions frequently. But in this case, there are decent telescope images, and I don't think the artist's impression we have conveys substantially different trustworthy information than the images (it's just higher "resolution"). The annesastronomynews.com source is clearly just a mirror, not the original release of the image. The image was presumably originally released with a CfA press release or educational materials (since it's credit to a CfA artist/public affairs officer), but I have failed to find that original release with a fair amount of online searching. We therefore have no indication what choices were in the composition of the image, particularly how to create finer detail than is available observationally and whether those nebulous rings about halfway out are meaningful or just made up.
 * In fact, the annesastronomynews.com source doesn't even note that it's an artist's impression (an IP editor guessed that by inference from the other works by David Aguilar and then confirmed it by email with the CfA public affairs office; not exactly a reliable source). So my discomfort is that we're using an image third hand without knowing much of anything about it except that the source we got the image from provides a very inadequate description, and no better description is available. When we can find images (DSS or SDSS) which we understand better, I think that's preferable. —Alex (Ashill &#124; talk &#124; contribs) 13:30, 11 May 2015 (UTC)
 * If we're going to go with SDSS imagery under fair use, might as well use this from the SDSS-II survey. Whatever is eventually decided, just let me know and I'll handle the transfer and fair use rationaling. — Huntster (t @ c) 06:44, 11 May 2015 (UTC)
 * Support - Reliable and a clear telescopic view of the galaxy. -- Chamith   (talk)  07:05, 11 May 2015 (UTC)
 * I think that's the same image I proposed just with a different zoom; they certainly look very similar. I don't have a strong feeling one way or the other. —Alex (Ashill &#124; talk &#124; contribs) 13:18, 11 May 2015 (UTC)
 * Support - Photometric > artist's conception.  ~ Tom.Reding (talk ⋅contribs ⋅dgaf)  13:29, 11 May 2015 (UTC)
 * Support the use of the SDSS image over an artists impression. - Parejkoj (talk) 15:41, 11 May 2015 (UTC)

It's been two weeks and nothing but support, so I think going with the SDSS-II image from wikisky has consensus. —Alex (Ashill &#124; talk &#124; contribs) 20:25, 26 May 2015 (UTC)
 * , rgr, will take care of it later tonight. — Huntster (t @ c) 02:16, 27 May 2015 (UTC)
 * Image has been uploaded to File:IC 1101 by SDSS-II.jpg and inserted into the article. File:IC 1101, telescope image.jpg has been tagged as orphaned fair use. — Huntster (t @ c) 11:17, 27 May 2015 (UTC)
 * Thanks. The new image is a significant improvement, I think. —Alex (Ashill &#124; talk &#124; contribs) 13:08, 27 May 2015 (UTC)

Size
Isn't IC 1101 over 4,000,000 ly in radius? Here it says 218,000 ly. Please clarify this.

Thanks!

PNSMurthy (talk) 02:42, 23 July 2020 (UTC)


 * See the discussion above: there's a lot of incorrect secondary sources, and we want to state consistent definitions for "size" across wikipedia. - Parejkoj (talk) 16:01, 23 July 2020 (UTC)
 * Very well Parekjkoj. I understand there are some things that are hard to identify as reliable. Size is one of them, and many people exaggerate size for reasons I don't quite know. I may as well cite a youtube video saying the largest known galaxy is 'GBYSDZGyuadtquadytyiu' I guess. I think, that, if IC 1101's size is so shady, we should temporarily remove it until the size is confrimed?PNSMurthy (talk) 02:32, 28 July 2020 (UTC)


 * We include what we can that reliable sources tell us. What is in the article is the most recent scientific data; if we remove it waiting for "more accurate" data to come out, we could be waiting many years. Astronomy is always going to involve the slow improvement of knowledge, so it tends to be ever changing. — Huntster (t @ c) 11:01, 28 July 2020 (UTC)


 * Very well. I understand the largest galaxies are not exactly the most popular subject for astronomers. We should leave the most accurate size on the sheet. By the way, is the effective radius strictly for the inner galaxy, or the inner galaxy and halo? Uson et all gives 4,000,000 lightyears.PNSMurthy (talk) 02:37, 29 July 2020 (UTC)


 * The inner galaxy. The halo, by its nature, is very difficult to pin down its extent. That's part of the problem...the original multi-million ly radius included the halo, but since halos aren't typically included in measurements for other galaxies, does it make sense to use it here? Because it is so distant and the halo so bright, it was hard to tell where the galaxy proper ended, and the halo began. — Huntster (t @ c) 05:07, 29 July 2020 (UTC)


 * Thank you for clarifying:)PNSMurthy (talk) 05:35, 29 July 2020 (UTC)

Removal of 'Discovery' section
Why was the section 'Discovery' removed on 9 December 2020 with the comment it is superfluous? IMO this is relevant information - I have therefore undone this edit. 2A02:C7D:8916:3F00:404B:DAFE:3792:BC24 Blammy1 (talk) 14:08, 10 December 2020 (UTC)
 * The only relevant part and well-cited of that paragraph is the discovery date by Herschel. Discussion of its inclusion in the New_General_Catalogue doesn't add anything; of course it's in the IC catalog, that's in the name! The universeguide.com cite does not provide links to where it got the various data from and has a bunch of nonsense (e.g. "Naked Eye Visibe: Requires 8m Telescope" is totally wrong given that Herschel was able to see it, and it quotes the incorrect 1.9 Mly radius). Rooting around there briefly, I'd say that page is definitely not a reliable source for anything astronomical. The subsequent two sentences add nothing beyond recapitulating the results of the Great Debate, which had nothing to do with this object in particular, and the added arxiv citation has nothing to do with this point. I've removed the paragraph again. If there are reliable sources that do say something about its history, please include them. - Parejkoj (talk) 17:52, 11 December 2020 (UTC)

Parejkoj If you're unhappy with it, rather than deleting the whole section, why don't you rewrite it to make it relevant? I'm sorry, but IMO it seems a very heavy-handed and lacking response from you. Blammy1 (talk) 21:16, 12 December 2020 (UTC)

Replace b/w lead image with color image


The current lead image is b/w, thus can not properly illustrate: Like most large galaxies, IC 1101 is populated by a number of metal-rich stars, some of which are seven billion years older than the Sun, making it appear golden yellow in color.

Candidates are listed on the right. 51Oq (talk) 06:41, 9 February 2021 (UTC)

The core problem, I think, is that uncited and incorrect statement, not the image. The appearance of a galaxy depends on the false color scheme chosen to represent filters; “golden yellow” is way too specific to describe the color of a galaxy. But I think the SDSS image does look good and using that would be fine. —Alex (Ashill &#124; talk &#124; contribs) 07:36, 9 February 2021 (UTC)

Largest core of any galaxy?
I have noticed this article about IC 1101's core. Link: [] Any Thoughts?

New updates from NED
This is just a quick update on IC 1101 (as part of the work I'm doing for the revival of the list of largest of largest galaxies, check it out here if you're interested.) I think that this is a major one that it deserves to be mentioned here.



New quoted redshift: 0.021488 +/- 0.000009 New distance: 90.7 +/- 6.4 Mpc (295.68 +/- 20.86 light years)

Which is just ~30% of the distance quoted now (1.07 billion light years)

Looking at the history of redshift measurement 1101&img_stamp=YES&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1&of=table here, it appears its redshift varies between ~0.021 (in 21-cm hydrogen) and ~0.078 (optical filter, clueless if it was spectroscopic). Probably a weird spectrum, so I'll change it for now. SkyFlubbler (talk) 21:37, 5 July 2022 (UTC)


 * SkyFlubbler, I've contacted NED about this, but wasn't able to followup. The radio and optical spectroscopic redshift measurements are quite different; from the brief literature search I did, there's only one actual measurement in each case, and then a bunch of papers citing one or the other. I personally would trust the optical spectrum more than a 21cm radio survey, which could be confused by a foreground gas cloud. This needs some actual expertise to disentangle, and likely needs someone to contact the authors of Springob et. al, (2005) for details of their analysis. I wouldn't change the redshift we list here. - Parejkoj (talk) 16:49, 6 July 2022 (UTC)


 * I see. Then in this case, I think we should give values for both (for matters of context), and then just cite the value of the optical redshift over the other ones. SkyFlubbler (talk) 00:17, 7 July 2022 (UTC)

I think you should do it already. The Space Enthusiast (talk) 16:00, 9 July 2022 (UTC)


 * Stepping aside though, what makes me not want to change this newer value is IC 1101's magnitude (14.71), which is not consistent for a galaxy that is 1.07 billion light years away (a luminous cD galaxy at this distance has a magnitude of usually ~15.5). Unless IC 1101 is a Seyfert or an exceptionally luminous cD, I have doubts with the older redshifts. SkyFlubbler (talk) 03:44, 17 July 2022 (UTC)

We have to contact the authors then. The Space Enthusiast (talk) 08:36, 17 July 2022 (UTC)

I see you're going through and changing values computed from the z~0.077 distance from optical/near-IR spectroscopy to the definitely incorrect 21cm redshift measurement. I should have caught this earlier: IC 1101 is the central galaxy of Abell 2029, which absolutely, without any qualification, has a redshift of ~0.077 (e.g. Faber & Dressler (1977), Struble & Rood (1999), and even a dozen or so spectra of cluster members from SDSS). We can talk with NED and the authors of Springob et. al, (2005) about that 21cm measurement, but please revert your changes to the distance of this object and related parameters: all of those values are incorrect, and you're doing what amounts to WP:OR here. - Parejkoj (talk) 06:22, 23 July 2022 (UTC)


 * I disagree that it's WP:OR though, because we have references to support it. Definitely the z=0.077 was a consensus among those that used optical spectroscopy, but the value of z=0.021 was not new, dating back to this paper in 1997. This reading has been remarked as "Quality good" in the comment (pertaining to the 2005 Springob paper, which I think is independent from the 1997 one, see 1101&img_stamp=YES&hconst=67.7&omegam=0.31&omegav=0.69&corr_z=1&of=table#No9 here). At this point, though, I don't think it would be possible to verify these numbers as due to how old they were. But it's simply setting a bad tone to dismiss these numbers as "incorrect" without showing them as such.


 * I changed it back to the older setting (primarily because when I checked ACO 2029 at NED, it follows the older redshift, and SIMBAD also uses the z=0.077 value pertaining to a 2014 paper), so that solves it. But the stark contrast of IC 1101 between the values of other A2029 galaxies, more so its intrinsic properties, points more to IC 1101 being a foreground object rather than a cD galaxy in A2029. Only a quasar can have a visual magnitude of 13.2 from a distance of 1.07 Gly. I did not include this in the article, of course, for strictness purposes. SkyFlubbler (talk) 09:37, 23 July 2022 (UTC)
 * I know that you are an astronomer and I appreciate that, but how are the values incorrect? The Space Enthusiast (talk) 16:06, 23 July 2022 (UTC)

I may be sorry to restart this discussion, but I have been delving into IC 1101 and Abell 2029. One thing I remember is that the redshift placed IC 1101 at the center of Abell 2029. The Space Enthusiast (talk) 23:35, 16 February 2023 (UTC)

Orphaned references in IC 1101
I check pages listed in Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of IC 1101's orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.

Reference named "NED": From NGC 4365:  From Arp 271:  From NGC 4777:  From NGC 4343:  From NGC 4701:  From NGC 5806: </li> <li>From NGC 4780: </li> <li>From NGC 4380: </li> <li>From Abell 1835: </li> <li>From SDSS J1229+1122: </li> <li>From Abell 2147: </li> <li>From NGC 4918: </li> <li>From NGC 4746: </li> <li>From Abell 1689: </li> <li>From NGC 4643: </li> <li>From NGC 4845: </li> <li>From NGC 5619: </li> <li>From NGC 5030: </li> <li>From NGC 4866: </li> <li>From NGC 5575: </li> <li>From Abell 2029: </li> <li>From NGC 5384: </li> </ul>

I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT ⚡ 22:20, 5 July 2022 (UTC)

Halo size?
As we know, IC 1101's gigantic halo is commonly (incorrectly) quoted as the galaxy's size, thus making it widely known to the media and public. While the size of the halo is quoted to be 2 million light-years (600 kpc), citing Uson et al (1991)’s paper regarding the diffuse light within Abell 2029, I feel like Juan Uson’s other paper on Abell 2029 regarding IC 1101 is the actual source on the galaxy’s massive halo size. This is because I don’t see a diameter of the halo quoted in the other paper which has a “verification needed” sign near it on the page. Unfortunately, the paper is locked up, which means that I was unable to retrieve details from the paper, except for a mention of IC 1101’s halo being able to be traced out to 1 mega parsecs away from the galaxy’s center. This is interesting, so I am requesting somebody who has access to the paper to take a screenshot of the paper’s details so that we can add it to the article.


 * Note: you can't just use physical sizes in an article from the 90s, you have to start with angular sizes and appropriately scale them to the distance given the redshift, because the cosmological parameters used in those papers are incorrect. - Parejkoj (talk) 22:45, 8 January 2023 (UTC)


 * Thanks. Just curious, why are they incorrect?--The Space Enthusiast (talk) 03:16, 9 January 2023 (UTC)
 * Because the cosmology used in those papers was before the discovery of dark energy, so the redshift-distance relation they use is wrong, and thus the angular diameter to physical size conversion is wrong. This is related to the original problem with this article (just using the physical size, without correcting for a more modern cosmology). - Parejkoj (talk) 17:03, 9 January 2023 (UTC)


 * Thanks. I think that there needs to be more research on galaxy sizes. The Space Enthusiast (talk) 17:35, 9 January 2023 (UTC)

Regarding Donzelli et al. (2011)
I just have an inner gut feeling that we should not trust the values of this paper, which gave a ~2.8 million light year diameter for IC 1101. For one it gives either very small or very large values, which makes most galaxies cited in the paper as dwarf galaxies, while others giants, despite some being prominent clusters.

The effective radius might be an intracluster light radius. As an example Abell 2589 was listed at 725.91 kpc despite the cluster having no BCG whatsoever. I believe they measured NGC 7647 which is just in the vicinity, which is actually a foreground unrelated galaxy. On the second table Abell 3562, whose central galaxy is ESO 444-72, was listed at a ridiculous ~1160 kpc, which is just nuts (the galaxy is 196 kpc diameter at NED). SkyFlubbler (talk) 02:57, 2 April 2023 (UTC)


 * Thanks. Dullo 2017 mentioned it. I might remove it now. The Space Enthusiast (talk) 04:30, 2 April 2023 (UTC)

Far too long + synth
This article has become severely bloated with WP:SYNTH links to survey papers and topics that apply to most large central galaxies in clusters. It doesn't need new topics added, it needs to be stripped down significantly. It's not a particularly special galaxy: the only reason it's particularly notable are the past incorrect articles about "the largest galaxy in the universe" and the fact that it's the central galaxy of a massive cluster. - Parejkoj (talk) 18:15, 20 April 2023 (UTC)
 * I have decided to remove my changes, so we can discuss them here. I can add them on articles related to brightest cluster galaxies, where you might deem them more appropriate. That being said, I don't think the incorrect articles saying that it is the largest galaxy in the universe account for all of its notability, since it is notable for having a rising velocity dispersion as stated in.


 * The galaxy is however still noteworthy beyond the bogus largest galaxy claims. It is a very luminous X-ray source, possesses one of the most massive black holes, and is a target of some studies on cold dark matter models. SkyFlubbler (talk) 03:45, 21 April 2023 (UTC)
 * I might have to agree. Of course there are galaxies larger than IC 1101, but that does not detract from the fact that it is still a very large and remarkable galaxy. Parejkoj's point stills stands however; I have undone much of my edits over the last month and decided to devote my collection of references to the "Observation history" section.


 * That being said, it is quite mind-boggling that the research papers saying IC 1101 is the largest galaxy just straight up ignore Oemler 1976 and Schombert 1988 as well as a 2018 Spanish study that show Abell 1413-BCG as being much larger than IC 1101 is. I know that Oemler 1976 uses the outdated 50 km/s/Mpc value for the Hubble constant (which inflates distances) and that the 3.5 Megaparsec radius for Abell 1413's BCG is likely the intracluster light (which is unbound to any galaxy), but the D25 diameters of IC 1101 and Abell 1413 show that the latter is almost two times larger, even though the former uses the Blue band of light while the latter uses the Red band of light. I might as well have opened a can of worms on how to organize Abell 1413, and whether we should inlcude Oemler 1976 or not. The Space Enthusiast (talk) 05:16, 21 April 2023 (UTC)

Possibly too long
Hello. I am the editor who has recently expanded the article. Almost 2 weeks ago, User:Parejkoj suggested that my edits made this article too long, and thus I deleted my previous revisions of the article. I have slowly begun to re-add them however, and the page has become bloated again. I am not intentionally inflating the article, it's just that IC 1101 is a well-studied galaxy and I thought that the various studies on this galaxy need to have attention. I also expanded this galaxy's page so that its identity could be split away from the "largest galaxy".--The Space Enthusiast (talk) 19:53, 1 May 2023 (UTC)


 * It looks okay to me...idk tho User:Hamterous1 (discuss anything!🐹✈️) 11:49, 11 April 2024 (UTC)
 * I don't see it as inflated at all. It would be one thing if the article was spammy, but it discusses the scientific attributes and observation history. — Huntster (t @ c) 19:33, 20 April 2024 (UTC)
 * Me too User:Hamterous1 (discuss anything!🐹✈️) 21:28, 20 April 2024 (UTC)