APOD: NGC 4565: Galaxy on Edge (2022 May 26)

[APOD Robot]

NGC 4565: Galaxy on Edge

Explanation: Magnificent spiral galaxy NGC 4565 is viewed edge-on from planet Earth. Also known as the Needle Galaxy for its narrow profile, bright NGC 4565 is a stop on many telescopic tours of the northern sky, in the faint but well-groomed constellation Coma Berenices. This sharp, colorful image reveals the galaxy's boxy, bulging central core cut by obscuring dust lanes that lace NGC 4565's thin galactic plane. NGC 4565 itself lies about 40 million light-years distant and spans some 100,000 light-years. Easily spotted with small telescopes, sky enthusiasts consider NGC 4565 to be a prominent celestial masterpiece Messier missed.

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[Ann]

NGC 4565. Image: Michael Sherick.

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Let me begin by passing a verdict: NGC 4565 is a quite yellow galaxy ███, and not very colorful at all.

Let me show you a few pictures of NGC 4565 to prove my point!

NGC 4565 by ESO.

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NGC 4565 by SDSS and Donald Pelletier.

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NGC 4565 by Peter Bresseler.

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All right. There are bluer pictures of NGC 4565. The picture of NGC 4565 by NASA's now defunct ultraviolet-detecting space telescope GALEX proves that there are (mostly moderate A- and B-type) ultraviolet stars in the dust lane of NGC 4565:

Moderate blue stars of spectral classes A and B in the dust lane of NGC 4565. Image: GALEX.

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Ultraviolet stars, many of spectral class O, in NGC 4631. Image: GALEX.

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So there are blue stars in NGC 4565, but they are not very bright, and they are not found in large clusters. And there are no large bright pink emission nebulas, even though there are undoubtedly small faint emission nebulas there.


Let's compare NGC 4565 with NGC 4631! What a difference!

NGC 4631 by SDSS. 'Galaxie de la Baleine' means 'Whale galaxy'. Note the greenish splotches, which are emission nebulas.

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NGC 4631 by Adam Block.

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NGC 4565 is a much larger galaxy than NGC 4631, but the latter is bursting with star formation.

Ann

[AVAO]

Let me begin by passing a verdict: NGC 4565 is a quite yellow galaxy ███, and not very colorful at all.

Ann

I totally agree with you. Today's APOD image is too colorful looking at the blue and red ends. In reality the galaxy is probably very similar to NGC 4594 (Sombrero Galaxy) and also quite inactive or one can say dead. The resemblance is best seen in infrared: an inactive outer dust ring and an "empty" center.


https://esahubble.org/images/opo0328b/
Credit:NASA/JPL-Caltech and The Hubble Heritage Team (STScI/AURA)

https://live.staticflickr.com/2883/3394 ... 9b45_h.jpg
https://commons.wikimedia.org/wiki/File ... pitzer.png
Credit:Serge Meunier
Compound Spitzer image made up of 4 Infrared exposure from the IRAC Map on the Spitzer space telescope.
The images used filters on the 3.6μm, 4.5μm, 5.8μm and 8.0μm bands.

[beryllium732]

How come NGC 4631 have so much higher star formation? How come it does have so much more bright pink emission nebulas? Dustlanes and the gas within them combine to create stars but not as effeciently as the pink nebulas which contains much more hydrogen and less dust?

[Ann]

Let me begin by passing a verdict: NGC 4565 is a quite yellow galaxy ███, and not very colorful at all.

Ann

I totally agree with you. Today's APOD image is too colorful looking at the blue and red ends. In reality the galaxy is probably very similar to NGC 4594 (Sombrero Galaxy) and also inactive or one can say dead. The resemblance is best seen in infrared: an inactive outer dust ring and an "empty" center.


https://esahubble.org/images/opo0328b/
Credit:NASA/JPL-Caltech and The Hubble Heritage Team (STScI/AURA)

https://live.staticflickr.com/2883/3394 ... 9b45_h.jpg
https://commons.wikimedia.org/wiki/File ... pitzer.png
Credit:Serge Meunier
Compound Spitzer image made up of 4 Infrared exposure from the IRAC Map on the Spitzer space telescope.
The images used filters on the 3.6μm, 4.5μm, 5.8μm and 8.0μm bands.

Thanks for agreeing with me, AVAO!

Unfortunately, I have to disagree with you, at least a little.

NGC 4565 is not "red and dead", and we can see two signs that it is not.

Let's look at the Spitzer/Serge Meunier image of NGC 4565 again (and thanks for finding it, because I was unable to find it when I was googling):

NGC 4565 in infrared light. Image: Spitzer Space Telescope/Serge Meunier.

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As you can see, the dusty disk (shown in red) is clumpy. Such clumpiness suggests the presence of young star clusters and even ongoing star formation.

Compare the clumpy dust lane of NGC 4565 with the almost perfectly smooth dust disk of M104 in the Spitzer image posted by you. This nearly perfect smoothness strongly suggests that the disk has been left undisturbed by local perturbations for a long time. This is in turn suggests that the disk is not forming stars, at least not on any significant scale.


Let's compare the GALEX image of NGC 4565 with a tiny and blurry (sorry) GALEX image of M104:

NGC 4565 by GALEX.

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M104 GALEX.png

M104 by GALEX.

As you can see, the dust lane of NGC 4565 is blue in the GALEX image. This means that there are ultraviolet stars present everywhere in the dust lane. Note that A-type stars like Sirius and Vega are ultraviolet enough for the now-defunct GALEX detectors to react, and I insist that NGC 4565 shows no signs of really massive star formation, so the blue color of the dust lane doesn't mean that NGC 4565 is full of hot blue stars like the ultraviolet giants in Orion. Nevertheless, there are young stars in there, and GALEX proved it.

Compare the ultraviolet image of NGC 4565 with the ultraviolet image of M104. As you can see, there are no blue clumps or knots there at all. None. The dust lane is all dark, unlike the dust lane of NGC 4565, which is reasonably bright in ultraviolet. (A few relatively bright clumps can indeed be seen in the inner part of the dust disk of M104 in the GALEX image, but the color of these clumps is not blue. Their nature is ambiguous. They could be older clusters which are richer in stars than their background, but whose member stars don't emit any far ultraviolet light, so they are cooler than A-type stars.)

So, to conclude: Yes, M104 is red and dead. But NGC 4565 isn't. It is just a very yellow galaxy. Mellow yellow! But so is Andromeda. Really.

Ann

[bratislav]

I haven't seen this much overprocessed 4565 - perhaps ever. All of the detail in the dust line is simply "invented". You could have pretty much used a paintbrush. I don't know what the editors are thinking.

[Ann]

How come NGC 4631 have so much higher star formation? How come it does have so much more bright pink emission nebulas? Dustlanes and the gas within them combine to create stars but not as effeciently as the pink nebulas which contains much more hydrogen and less dust?

That is a good question that is hard to answer.

Stars are formed from gas, not from dust. But dust is a tracer of gas, because some amount of dust is always - at least in the nearby universe - mixed with the gas.

In order to form stars, the gas must be cool. It must be made to collapse and concentrate by some means. Dust helps the gas cool down, and there are various mechanisms that may cause gas to locally collapse. But it doesn't always happen.

This is AM 1316-241, a pair of non-interacting galaxies where the smaller spiral galaxy is seen in projection against the larger elliptical galaxy. The small spiral has an outer dust lane that is almost completely devoid of young stars and star formation. Credits: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and W. Keel (University of Alabama, Tuscaloosa)

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The outer dust lane of AM 1316-241 isn't forming stars, even though the raw materials for star formation appear to be present.

Interactions with other galaxies is often a good way to compress gas and make it collapse and form stars. Take a look at this image of NGC 4449 and its very tiny companion:

NGC 4449 is a dwarf galaxy similar to the Large Magellanic Cloud. It is forming stars at a furious rate. Note that it is interacting with a very tiny companion - faint elongated reddish streak at lower right - whose presence is undoubtedly stirring things up in NGC 4449. Image: R. Jay GaBany. Insert: Subaru Telescope.

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Like NGC 4449, NGC 4631 is also interacting with a companion, and this interaction is certainly driving its star formation. However, star formation can only happen if a galaxy has enough raw material, and sometimes they don't:

NGC 4631, the Whale Galaxy, and its small companion, NGC 4627. Image: SDSS.

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Dry merger IC 1181 IC 1178 Detlef Hartmann.png

A "dry merger" in the Hercules Cluster of galaxies. Image: Detlef Hartmann.

The two galaxies in the Hercules Cluster, IC 1178 and IC 1181, have undoubtedly lost their gas and dust through previous interactions and mergers in the galaxy cluster that they belong to. They can form no more stars.

As for NGC 4565, it looks extremely "undisturbed" to me. I guess that it is mostly just sitting there, spreading its disk wider and wider, lazily forming "Siriuses" and "Vegas" in its dust lane.

Sorry, that is the best explanation I can come up with!

Ann

[AOctavio]

TOPAZ! Why are so many APODs going crazy with Topaz?! It feels like the entire concept of an APOD is being ruined, using these artificial AI sharpening tools turns the image into a water-color painting, not an astronomical image! All of the detail here is entirely fake and undermines the astronomy community who actually tries to use actual data... Very disappointed.

[AOctavio]

I haven't seen this much overprocessed 4565 - perhaps ever. All of the detail in the dust line is simply "invented". You could have pretty much used a paintbrush. I don't know what the editors are thinking.

It feels like it's becoming a trend to put overprocessed fake images on APOD lately... quite sad.

[orin stepanek]

Needle_Galaxy_4-7-22.jpg

APOD,sky enthusiasts consider NGC 4565 to be a prominent celestial masterpiece Messier missed.

Maybe Messier didn't miss it; He may not have it thought to be a
comet! Anyway I do think it is quite a masterpiece! I love this
beauty! Kudos also to the photographer!

[MarkBour]

Let me begin by passing a verdict: NGC 4565 is a quite yellow galaxy ███, and not very colorful at all.
. . .
So there are blue stars in NGC 4565, but they are not very bright, and they are not found in large clusters. And there are no large bright pink emission nebulas, even though there are undoubtedly small faint emission nebulas there.
. . .
Ann

Thanks for the info!
If a galaxy is yellow and relatively quiet, do you conclude that it's older than the more active star-forming galaxies, or is it just that it has less gas, or maybe it has plenty of gas, but less of it is "in the mood" for star formation?

[beryllium732]

How come NGC 4631 have so much higher star formation? How come it does have so much more bright pink emission nebulas? Dustlanes and the gas within them combine to create stars but not as effeciently as the pink nebulas which contains much more hydrogen and less dust?

That is a good question that is hard to answer.

Stars are formed from gas, not from dust. But dust is a tracer of gas, because some amount of dust is always - at least in the nearby universe - mixed with the gas.

In order to form stars, the gas must be cool. It must be made to collapse and concentrate by some means. Dust helps the gas cool down, and there are various mechanisms that may cause gas to locally collapse. But it doesn't always happen.

This is AM 1316-241, a pair of non-interacting galaxies where the smaller spiral galaxy is seen in projection against the larger elliptical galaxy. The small spiral has an outer dust lane that is almost completely devoid of young stars and star formation. Credits: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and W. Keel (University of Alabama, Tuscaloosa)

---

The outer dust lane of AM 1316-241 isn't forming stars, even though the raw materials for star formation appear to be present.

Interactions with other galaxies is often a good way to compress gas and make it collapse and form stars. Take a look at this image of NGC 4449 and its very tiny companion:

NGC 4449 is a dwarf galaxy similar to the Large Magellanic Cloud. It is forming stars at a furious rate. Note that it is interacting with a very tiny companion - faint elongated reddish streak at lower right - whose presence is undoubtedly stirring things up in NGC 4449. Image: R. Jay GaBany. Insert: Subaru Telescope.

---

Like NGC 4449, NGC 4631 is also interacting with a companion, and this interaction is certainly driving its star formation. However, star formation can only happen if a galaxy has enough raw material, and sometimes they don't:

NGC 4631, the Whale Galaxy, and its small companion, NGC 4627. Image: SDSS.

---

Dry merger IC 1181 IC 1178 Detlef Hartmann.png

A "dry merger" in the Hercules Cluster of galaxies. Image: Detlef Hartmann.

The two galaxies in the Hercules Cluster, IC 1178 and IC 1181, have undoubtedly lost their gas and dust through previous interactions and mergers in the galaxy cluster that they belong to. They can form no more stars.

As for NGC 4565, it looks extremely "undisturbed" to me. I guess that it is mostly just sitting there, spreading its disk wider and wider, lazily forming "Siriuses" and "Vegas" in its dust lane.

Sorry, that is the best explanation I can come up with!

Ann

Thank you that's a very good explanation together with pictures! I am satisfied!

[johnnydeep]

TOPAZ! Why are so many APODs going crazy with Topaz?! It feels like the entire concept of an APOD is being ruined, using these artificial AI sharpening tools turns the image into a water-color painting, not an astronomical image! All of the detail here is entirely fake and undermines the astronomy community who actually tries to use actual data... Very disappointed.

TOPAZ? You mean this TOPAZ - https://www.topazlabs.com? How do you know that was used? There's no sign of that I can find either in the image details at astrobin or in the metadata in the image itself, which says it was last processed using Adobe Photoshop 23.1.

But as long as a "paintbrush" isn't actually used, I see no problem bringing out details that are really there, but that we wouldn't see otherwise. Almost all astrophotography does that to one degree or another.

I'm hoping the photo author is reading this and will weigh about what additional he may have done to process the image. Personally I think it looks lovely, but what do I know.

[AOctavio]

To the trained eye, it's quite obvious. I've used Topaz AI for the sharpening of DSO images before and it yields the exact same results in terms of the detail on dust lanes.
Just because the metadata editor says it's last been opened in PS, it doesn't mean that Topaz wasn't used. My processing routine for data is a constant cycle between Pixinsight and Photoshop, just because I last used PS, it means nothing.

[Ann]

Let me begin by passing a verdict: NGC 4565 is a quite yellow galaxy ███, and not very colorful at all.
. . .
So there are blue stars in NGC 4565, but they are not very bright, and they are not found in large clusters. And there are no large bright pink emission nebulas, even though there are undoubtedly small faint emission nebulas there.
. . .
Ann

Thanks for the info!
If a galaxy is yellow and relatively quiet, do you conclude that it's older than the more active star-forming galaxies, or is it just that it has less gas, or maybe it has plenty of gas, but less of it is "in the mood" for star formation?

I don't think we should describe galaxies as "older" or "younger", because I think that almost all at least moderately large galaxies are very old. That is to say that their oldest member stars are probably as old as the globular clusters, 10-12 billion years old, or even older.

Starburst galaxy I Zwicky 18. Credit: HST/NASA/ESA

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Wikipedia wrote:

I Zwicky 18 is a blue compact dwarf galaxy located about 59 million light years away in the constellation Ursa Major...

Studies at the Palomar Observatory some 40 years ago led astronomers to believe that the galaxy erupted with star formation billions of years after its galactic neighbours. Galaxies resembling I Zwicky 18's youthful appearance are typically found only in the early universe. Early observations with the Hubble Space Telescope suggested an age of 500 million years old for I Zwicky 18...

Later observations with the Hubble Space Telescope found faint and old stars contained within the galaxy, suggesting its star formation started at least one billion years ago and possibly as much as ten billion years ago. The galaxy, therefore, may have formed at the same time as most other galaxies.

So I don't think that galaxies are young. They are all old. The only exceptions that I can think of are the dwarf galaxies that condense out of the wreckage of tidal tails thrown out by larger galaxies in the throes of ongoing mergers or collisions:

Tadpole Galaxy with blue knots in tail.png

The large blue clusters in the tidal tail of the Tadpole Galaxy
will evolve into future dwarf galaxies.

But with the exception of newly formed tidal wreckage dwarf galaxies, galaxies are not young, but old. The question is whether they are still forming stars, and if they are, how vigorously they are doing so.

Sometimes it is very hard to understand why galaxies suddenly start forming a tremendous amount of stars.

Unusual starburst galaxy NGC 1313. Image: Rob Gendler.

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Consider starburst galaxy NGC 1313.

APOD Robot wrote:

Why is this galaxy so discombobulated? Usually, galaxies this topsy-turvy result from a recent collision with a neighboring galaxy. Spiral galaxy NGC 1313, however, appears to be alone. Brightly lit with new and blue massive stars, star formation appears so rampant in NGC 1313 that it has been labeled a starburst galaxy.

Weird, eh? This galaxy is all alone, and yet it is absolutely tormented and bent all out of shape because of its tremendous star formation. Perhaps it has collided with a clump of dark matter?

Maybe. But I think it is equally likely that NGC 1313 has discombobulated itself all by itself, by having its enhanced star formation at both ends of the bar suddenly turn into an almost "runaway" starburst, again at both ends of the bar. And because of the galaxy's obvious low mass, the tremendous forces of this "simultaneous double-sided" starburst may have severely unbalanced the galaxy and led to its contorted shape.

But other galaxies that sit quietly all alone do indeed form stars slowly. That is the case for the "UFO galaxy", NGC 2683:

NGC 2683. Credit: NASA.

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Wikipedia wrote:

NGC 2683 is a field spiral galaxy in the northern constellation of Lynx. It was nicknamed the "UFO Galaxy" by the Astronaut Memorial Planetarium and Observatory...

It is also both smaller and less luminous than the Milky Way with very little neutral hydrogen or molecular hydrogen and a low luminosity in the infrared, which suggests a currently low rate of star formation.

NGC 2683 is rich in globular clusters, hosting about 300 of them, twice the number found in the Milky Way.

NGC 2683 appears to be located in a cosmic void, where there are few galaxies:

Michael König and ‎Stefan Binnewies wrote in The Cambridge Photographic Atlas of Galaxies:

The SA(rs)B galaxy NGC 2683 is about 6^o east of the star Alpha Lyncis. It is part of the sparse environment of the Lynx-Cancer Void, a nearby filament of about 100 galaxies, many of them dwarfs.

So it would appear that NGC 2683 is located in a relatively unusual and sparse environment. Its large number of globulars suggests it has undergone several mergers in the past, and its low levels of neutral and molecular hydrogen suggests it has lost or used up much of its gas during its mergers. For now, it appears to be "quiet".

The reason why I brought up NGC 2683 is that it reminds me a little of NGC 4565, which strikes me as very "quiet" indeed, more so than NGC 2683. NGC 4565 looks so undisturbed to me.

As to why NGC 4565 is forming stars slowly, I don't know. It could be because it has low levels of neutral and molecular gas. But in my opinion, it could also be because for whatever reason, it hasn't had the necessary triggers to convert its gas to stars in massive bursts of star formation.

As to why some galaxies just start bursting with star formation while others sit rather quietly, I don't know. Consider NGC 6822:

NGC 6822. Credit: Image Credit & Copyright: Data - Martin Pugh, Processing - Mark Hanson

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I'm all but sure that I have read that NGC 6822 sits in a large reservoir of gas, yet it isn't bursting with star formation. Yes, it is forming stars, but compared with I Zwicky 18 (which is interacting with another galaxy) or NGC 1313 (which is not), its rate of star formation is not too impressive. Don't ask me why this is so!

And that is all I have to say on the matter.

Ann

[AVAO]

NGC 4565 in infrared light. Image: Spitzer Space Telescope/Serge Meunier.

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As you can see, the dusty disk (shown in red) is clumpy. Such clumpiness suggests the presence of young star clusters and even ongoing star formation.

Ann

Good point! All right then - you're right: NGC 4565 and the M104 (Sombrero Galaxy) are not really comparable. An interesting detail is the fact that when IR and UV are superimposed, you can see that the bright stars from GALEX in UV are practically all outside SPITZER's dust ring in IR around the center of the galaxy...


https://live.staticflickr.com/65535/521 ... 9553_k.jpg
Jac Berne (flickr)

[rstevenson]

To the trained eye, it's quite obvious. I've used Topaz AI for the sharpening of DSO images before and it yields the exact same results in terms of the detail on dust lanes.
Just because the metadata editor says it's last been opened in PS, it doesn't mean that Topaz wasn't used. My processing routine for data is a constant cycle between Pixinsight and Photoshop, just because I last used PS, it means nothing.

Is this what you’re referring to, the wormy looking blobs? …

0D980911-38BB-4AD7-A837-F2DBB7E6487F.png

Can you provide a comparison image of the same galaxy processed in some other way?

Rob

[MarkBour]

Ann -- Thanks for this additional post, as well, once again chock-full of enlightening information.

[VictorBorun]

NGC 4565 in infrared light. Image: Spitzer Space Telescope/Serge Meunier.

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As you can see, the dusty disk (shown in red) is clumpy. Such clumpiness suggests the presence of young star clusters and even ongoing star formation.

Ann

Good point! All right then - you're right: NGC 4565 and the M104 (Sombrero Galaxy) are not really comparable. An interesting detail is the fact that when IR and UV are superimposed, you can see that the bright stars from GALEX in UV are practically all outside SPITZER's dust ring in IR around the center of the galaxy...


https://live.staticflickr.com/65535/521 ... 9553_k.jpg
Jac Berne (flickr)

is this NGC 4565 galaxy an Andromeda all over again: an IR-bright brown dusty ring about the core and a UV young star clumpy belt about the IR ring?
There may be a third ring, an IR-dark and starless cold dusty ring, but how to see it — in radio? against a backlight?