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I agree

Misuse of the term "IFN"

WesChilton
17 Oct, 2018 19:18
I'm starting to see a lot of imagers misuse the term "IFN" by adding it to their image titles inappropriately. Yes, I realize that "IFN" is the new whiz-bang term that gets clicks and likes, but if you are going to claim you captured IFN then you had better be sure that you know what you are talking about!

IFN stands for Integrated Flux Nebula. This term was given to clouds of mostly dust, hydrogen and carbon monoxide gases that exist OUTSIDE the Milky Way and are lit by the Integrated Flux, or the total accumulated light of all the stars in the Milky Way. It is strictly an extra-galactic phenomena and not used to describe more common gas or dust clouds that reside within the Milky Way.

https://en.wikipedia.org/wiki/Integrated_Flux_Nebula

So when someone posts images of M45 and claims to have captured IFN, they haven't and the term is being used incorrectly. The gas clouds surrounding M45 are primarily lit by the stars of the Pleiades and NOT from the total flux of the Milky Way, and are therefore a reflection nebula and not IFN.

The same goes for Vdb objects, the dust in the Taurus Molecular Cloud, and the dark dust lanes in and around the Milky Way. None of those are IFN.

Now that you know what IFN actually is… go look for it around the Polaris region, M81/M82 and other areas outside of our galaxy. You will find that true IFN is much more difficult to capture than the brightly lit gas clouds of M45.

Lets all strive to be accurate in our identification of astronomical features in our images for the education and benefit of everyone, and not engage in sensationalist tactics to get likes, please.

Thank you! smile
jeffbax
17 Oct, 2018 19:41
I agree. Astronomy, is a science and uses an accurate vocabulary. Even if some artistic approach is possible, the description of the objects should be precise.
Jf
Die_Launische_Diva
17 Oct, 2018 22:37
Unfortunately the Wikipedia article is terse. Also the link to Steve Mandel's web page does not work anymore.

If you have access to Sky & Telescope Magazine, I encourage you to read the article of Mel Bartels, "Herschel's Ghosts" (Sky & Telescope, April 2017, page 30)

Here is the beginning of the article:

WE SEE OUR GALAXY, the Milky Way, as a band of light stretching across the sky. There’s a ghostly aspect to it; faint streamers of gas and dust extend far above and below the galactic plane, reaching the galactic pole. This galactic cirrus — twisted clouds of interstellar dust particles at high galactic latitudes first observed in the far infrared in 1983–84 by the Infrared Astronomy Satellite (IRAS) — glows in the dim red region of the spectrum. But the dust also reflects blue light from countless millions of stars, as shown by amateur astronomer Steve Mandel in 2004. Mandel noticed the subtle blue glow of the spooky dust tendrils associated with M81 and M82 and captured it in images. These images, which formed the basis of his Unexplored Nebula Project (galaxyimages.com/UNP1.html), demonstrated that the dusty interstellar medium could be seen not only in the far infrared, but in visible light as well.

Mandel called these clouds Integrated Flux Nebulae (IFN), and, taking their cue from his work, many amateur astronomers use this term whether referring to galactic cirrus or dusty interstellar medium (ISM) in the galactic plane. Professional astronomers distinguish more carefully between the two, though the boundary between them is somewhat, well, nebulous. ISM, the dust and gas between the stars, is distributed throughout our galaxy, but can be found relatively close by — say 200 light-years from us at its nearest — in the galactic plane. Galactic cirrus, on the other hand, technically lies at high galactic latitudes (above and below the zodiac) and thousands of light-years distant.

Whatever you choose to call it, you may be surprised to learn that you can see it with amateur observing equipment. […]

According to the author, there is galactic cirrus near* M45, the so-called Pleiades Bubble.

From my own recent experience, it is not that difficult to capture the galactic cirrus clouds near* Polaris. You just need an f/2 lens and a total of two hours of exposure smile

(*) In terms of angular separation.
Edited 21 Oct, 2018 08:57
whwang
18 Oct, 2018 02:50
This is an interesting topic.  As a professional research astronomer, I have never heard about the term "integrated flux nebula" in professional astronomy.  I hear about it a lot in amateur astronomy over the years. So this thread got me interested, and I did some research.

PART I

First, let's assume Steve Mandel is the authority about this and the wiki page correctly quoted him.  Under such criteria, we can see that the IFNs are "high galactic latitude nebulae…."  It did not mention "extragalactic" anywhere.  "High galactic latitude" can still be well within the Galaxy.

Of course we can see that the same wiki page also says IFNs are "beyond the main body of the galaxy," but consider these three points:
1. "beyond the main body" doesn't mean it's extragalactic.  It can still be part of the galaxy, just not part of the main body.
2. "main body" is a poorly defined term.  In professional astronomy, we say Galaxy's "thin disk," "thick disk," "bulge," "gaseous disk," "stellar halo," "dark matter halo," etc.  We do not say "main body."  We want to be accurate, right?
3. That "beyond the main body of the galaxy" is just added by someone who edited that wiki page.  You and me can all edit it.  That doesn't really prove anything.

Considering all the above, based on the wiki page, I can't get a conclusion that IFNs have to be extragalactic.

PART II

In this part, I studied the term "integrated flux nebula" in the professional literature. My first thing to do was to check how this term is used in professional publications.  I did a keyword search in the NASA/Smithsonian Astrophysical Observatory database, and found 547 entries. You can see them in this link: https://tinyurl.com/ycun6zq8 . There are so many entries because astronomers talk about "integrated" a lot, they talk about "flux" a lot, and also "nebula" a lot.  Since I do not have infinite amount of time to check all the 547 entries., I just clicked into the first twenty entries to see their abstracts. Unfortunately, none of them talked about "integrated flux nebula." Instead of using them as keywords, I tried using them in the title search, and I only got three entries.  You can see the results here: https://tinyurl.com/yaoxugsf . Again, none of them are about "integrated flux nebula."

Next, I looked for Steve Mandel's professional publications. I searched the name "Mandel, S" in the same NASA/SAO database. You can see the results here: https://tinyurl.com/yddjoh5w . There are 10 entries. The first one was not by Steve, but the other 9 entries are. Among the 9, only four are professional publications, and the remaining five are just S&T articles.  Among the four that qualify as professional publications (1 Astrophysical Journal paper, two AAS presentations, and 1 Spitzer telescope proposal), none of them contains the term "integrated flux nebula" in their abstracts. Since only the ApJ paper has full text online, I can only check the full text of this one.  You can probably see the full text here: http://iopscience.iop.org/article/10.1086/587131/fulltext/ . Again, this paper does not use the term "integrated flux nebula." If you read the paper carefully, you will see that it did mention about clouds illuminated by the integrated radiation of the Milky Way. However, that's about "high-latitude interstellar clouds."  Since they are "interstellar," they can only be Galactic, not extragalactic.

BTW, the query page of the NASA/SAO database is here: http://adsabs.harvard.edu/abstract_service.html . You may be able to find something that I missed.

Based on the above, I think it is very fair to conclude that professional astronomers do not use the term "integrated flux nebula," not even in the only professional paper that Steve Mandel was associated with.  It's just an amateur term.  Of course, amateur astronomers can also invent terms.  But as I discussed in Part I, I see no evidence that Steve Mandel intended to use this term for extragalactic clouds.

BTW, the correct term in professional astronomy for thin reflection nebula (or mid-IR/far-IR emitting nebulas) in interstellar space is "cirrus."

Cheers,
Wei-Hao
Edited 18 Oct, 2018 03:40
WesChilton
18 Oct, 2018 04:43
Thanks very much for your comments, Wei-Hao!

I can’t argue with your points, especially concerning where exactly these IFN structures are. It was my understanding from the limited reading I have done, that they were considered to be outside the Milky Way. Evidently, that’s not a settled fact.

However, I would only say that, within the context of the term as I understand it, and even moreso lacking a validated scientific foundation, I still feel like it’s becoming a sort of a buzzword around Astrobin that is becoming diluted to mean “anything faint” that an imager captures in order to sound more impressive.

Being that, until recently, IFN was pretty much limited to gas and dust around Polaris, M81 & M82… which everyone seemed to agree was far away, very faint and tricky to capture… it seems like more and more I’m seeing the term used for more common, and arguably much easier to capture features… basically for likes.

I still think that is probably not a good thing.

I do appreciate the education on the term “cirrus”
smile
whwang
18 Oct, 2018 05:05
Hi Wes,

I agree with you that it's becoming a buzzword.  But it has some historical background: the advancements in sensor technology.  20 years ago when everyone pretty much just used film (and those who did use CCD only use tiny ones), I don't recall IFN being a popular word.  This is because amateur astrophotographers simply can't image them efficiently.  Now with large-format CCD and large CMOS DSLRs, imaging IFN is no longer impossible but still very interesting and challenging.  This is why the term becomes so popular.  I consider this a positive thing.

Scientifically, interstellar dust clouds have a continuous distribution.  On the Milky Way disk, because of the strong UV field, low-density dust clouds can easily be dissociated or even ionized.  So on the disk, we mostly only see dense molecular clouds.  Their surfaces also reflect the integrated star light, and thus they appear yellow. If we move above the disk, more low-density clouds can exist for a long time without being disrupted.  Their dust reflect star light and appear yellow.  They are probably the IFN in your mind.  But exactly where to draw the line is not trivial.  We can easily say the clouds see toward the Milky Way band are molecular clouds, and those around the polar region are IFN.  But in between, there are gray areas.  This is especially true if we consider that the Milky Way is a 3D object.  Thing that have high Galactic latitude can be indeed very close to the Galactic plane, and vice versa.  So it is really hard to say.  I personally want to be more tolerable on this.  As long as it is not directly in front of the Milky Way and it is yellowish, I am fine if people call it an IFN.

Cheers,
Wei-Hao
GerminianiMaicon
18 Oct, 2018 20:21
Hi Wes. I did not find any other image of Pleiades using the term IFN here in Astrobin. Just mine. So I believe you were referring to my image on this topic. I would just like to clarify that I am an Amateur Astrophotographer and that whenever possible I am learning new things. I just learned from you. It was never my intention to "hunt likes." I hope that was not your impression. Hugs from Brazil. Maicon Germiniani
grsotnas
19 Oct, 2018 00:46
Wei-Hao Wang
Hi Wes,I agree with you that it's becoming a buzzword.  But it has some historical background: the advancements in sensor technology.  20 years ago when everyone pretty much just used film (and those who did use CCD only use tiny ones), I don't recall IFN being a popular word.  This is because amateur astrophotographers simply can't image them efficiently.  Now with large-format CCD and large CMOS DSLRs, imaging IFN is no longer impossible but still very interesting and challenging.  This is why the term becomes so popular.  I consider this a positive thing.

Scientifically, interstellar dust clouds have a continuous distribution.  On the Milky Way disk, because of the strong UV field, low-density dust clouds can easily be dissociated or even ionized.  So on the disk, we mostly only see dense molecular clouds.  Their surfaces also reflect the integrated star light, and thus they appear yellow. If we move above the disk, more low-density clouds can exist for a long time without being disrupted.  Their dust reflect star light and appear yellow.  They are probably the IFN in your mind.  But exactly where to draw the line is not trivial.  We can easily say the clouds see toward the Milky Way band are molecular clouds, and those around the polar region are IFN.  But in between, there are gray areas.  This is especially true if we consider that the Milky Way is a 3D object.  Thing that have high Galactic latitude can be indeed very close to the Galactic plane, and vice versa.  So it is really hard to say.  I personally want to be more tolerable on this.  As long as it is not directly in front of the Milky Way and it is yellowish, I am fine if people call it an IFN.

Cheers,
Wei-Hao

Wei-Hao I learnt a lot from your posts on this topic!

I am interested in hunting those clouds from my limited conditions, and I captured some IFN around the Magellanic Clouds recently (the image is at https://astrob.in/370681/0/ ). Until that image I found IFN definition to be quite vague. My questions were partly gone when searching upon the topic to write my description from that image, and completely gone after your detailed response here.

I believe it could be to good use to the community if I post here a few references I found when researching on the topic, which are also on my Magellanic Clouds image description:

[3] R. Jay. GaBany cosmotography.com/images/galactic_cirrus.html [4] Alan Sandage, from bbastrodesigns. [5] Mel Bartels, “Herschel’s Ghosts” at bbastrodesigns.com/Herschels%20Ghosts.html ; [6] “Low Surface Brightness Imaging of the Magellanic System […];” Delgado et al. 2016 [at arxiv.org/abs/1602.04222]

Finally, my take on the topic and on those nebulae:

I believed the IFN to be a very faint nebulosity region, always photographed around M81, and near the North Pole. Eventually extending to M31 (Rogelio Bernal Andreo images are the 1st that come to mind). However, I found through Gerald Wechselberger that such nebulosity is also present in the South Celestial Pole - which I could (try) to capture from below the Equator!

Recently, I found R. Jay GaBany website (link above), and it explained a lot about those clouds to me. From that point on, I try to refer to them as Galactic Cirrus, and not only through the IFN term. Mel Bartels also has a very interesting article on the visual observation of such clouds. It is worth noting that probably the 1st visual observation of such regions was by Herschel, although at the time he simply referred to it as a [adapted quote from memory] "slight increase in the sky background brightness". Studies on the nature of the clouds (its chemistry, etc) were only carried out in the second half of the 20th Century. Finally, there is a nice survey on IRAS 100nm band that greatlly shows the Galactic Cirrus, and its presence at high galactic latitudes [recommend checking GaBany and also the software ALADIN for the complete survey ]. I believe Steve Mandel has "named" the cirrus as IFN in eartly 21st Century - very recently, and he has also compiled a nice list of very faint IFN regions, mostly near M81, in the Mandel-Wilson Catalogue.

I just love learning about new things, and I certainly learnt a lot here! I hope I added something valueable to the discussion, and please correct me in case I made a mistake! Once again thank you Wei-Hao for sharing the knowledge [and also Wes for starting the topic]

Best regards
Gabriel
WesChilton
23 Oct, 2018 17:01
Maicon Germiniani
Hi Wes. I did not find any other image of Pleiades using the term IFN here in Astrobin. Just mine. So I believe you were referring to my image on this topic. I would just like to clarify that I am an Amateur Astrophotographer and that whenever possible I am learning new things. I just learned from you. It was never my intention to "hunt likes." I hope that was not your impression. Hugs from Brazil. Maicon Germiniani
No worries! It was not you specifically I was referring to but more a general trend that I have begun to see moving in this direction. If it was just one person I would not have even thought to discuss it. It certainly isn't my intention to assume what an individual person's motives are. However when you see a trend among many, one starts to wonder why, and maybe my assumption was too strong. But given the unfortunate competitiveness sites with like buttons and imaging contests foster, it wouldn't be the first time people here did something for attention.

Anyway, clearly we are all learning here, myself included and this discussion is very interesting and helpful for all of us. smile

Cheers
Wes
WesChilton
23 Oct, 2018 17:10
I do like the term galactic cirrus for faint gas and dust clouds… but, after the course of this discussion, I do think that the "misuse" of IFN is more a problem with the vagueness of the term itself, and of course the connotation of the difficulty of imaging it, which makes it an appealing challenge and therefore an appealing term to apply to any faint dust target.

I think a funny irony is from that first article Gabriel linked…

"
The dark spaces between the stars is not a perfect vacuum; it's filled with molecules of gas and dust. The gas is mostly hydrogen and helium- the most abundant elements in the Universe. In addition, there are tiny dust grains released by mighty suns that ended their lives in titanic explosions, known as super nova, long ago in the distant past. The dust absorbs (blocks) and scatters (reflects) optical light. It also emits
FIR (Far Infra-Red) radiation at a wavelength between 100-250 microns. Because of this, interstellar dust is often considered a nuisance by astronomers."


Something we amateurs strive so hard to capture in our images is often considered a nuisance to professional astronomers! smile
GerminianiMaicon
23 Oct, 2018 20:34
Wes Chilton
Maicon Germiniani
Hi Wes. I did not find any other image of Pleiades using the term IFN here in Astrobin. Just mine. So I believe you were referring to my image on this topic. I would just like to clarify that I am an Amateur Astrophotographer and that whenever possible I am learning new things. I just learned from you. It was never my intention to "hunt likes." I hope that was not your impression. Hugs from Brazil. Maicon Germiniani
No worries! It was not you specifically I was referring to but more a general trend that I have begun to see moving in this direction. If it was just one person I would not have even thought to discuss it. It certainly isn't my intention to assume what an individual person's motives are. However when you see a trend among many, one starts to wonder why, and maybe my assumption was too strong. But given the unfortunate competitiveness sites with like buttons and imaging contests foster, it wouldn't be the first time people here did something for attention.

Anyway, clearly we are all learning here, myself included and this discussion is very interesting and helpful for all of us. smile

Cheers
Wes
Wes Chilton
Maicon Germiniani
Hi Wes. I did not find any other image of Pleiades using the term IFN here in Astrobin. Just mine. So I believe you were referring to my image on this topic. I would just like to clarify that I am an Amateur Astrophotographer and that whenever possible I am learning new things. I just learned from you. It was never my intention to "hunt likes." I hope that was not your impression. Hugs from Brazil. Maicon Germiniani
No worries! It was not you specifically I was referring to but more a general trend that I have begun to see moving in this direction. If it was just one person I would not have even thought to discuss it. It certainly isn't my intention to assume what an individual person's motives are. However when you see a trend among many, one starts to wonder why, and maybe my assumption was too strong. But given the unfortunate competitiveness sites with like buttons and imaging contests foster, it wouldn't be the first time people here did something for attention.

Anyway, clearly we are all learning here, myself included and this discussion is very interesting and helpful for all of us. smile

Cheers
Wes

Thanks Wes. we are all and always  learning! Hugs from brazil! Maicon Germiniani
 
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