APOD: NGC 1365: Majestic Island Universe (2024 Feb 01)

[APOD Robot]

NGC 1365: Majestic Island Universe

Explanation: Barred spiral galaxy NGC 1365 is truly a majestic island universe some 200,000 light-years across. Located a mere 60 million light-years away toward the faint but heated constellation Fornax, NGC 1365 is a dominant member of the well-studied Fornax Cluster of galaxies</a>. This sharp color image shows the intense, reddish star forming regions near the ends of the galaxy's central bar and along its spiral arms. Seen in fine detail, obscuring dust lanes cut across the galaxy's bright core. At the core lies a supermassive black hole. Astronomers think NGC 1365's prominent bar plays a crucial role in the galaxy's evolution, drawing gas and dust into a star-forming maelstrom and ultimately feeding material into the central black hole.

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[Ann]

Oh yeahhh!!! I saw Jean-Baptiste Auroux and Mike Selby's picture of NGC 1365 in the Recent Submissions thread just yesterday, and I thought it looked great!

NGC 1365: Majestic Island Universe. Image Credit & Copyright: Processing - Jean-Baptiste Auroux, Data - Mike Selby

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And it's lovely to see such a beautiful LRGB + Hα portrait of a starforming spiral galaxy, so that it can really strut its stuff on the galactic catwalk! I love the beautiful shape and the hues of yellow, pink and blue of this galaxy!


When I first saw a picture of this iconic galaxy - it was really long ago, and the picture was in black and white - I was unimpressed. How weird it looked! There was a very elongated fat central "belt" and then, from one end of this long belt, there was one straight arm up, and from the other end, one straight arm down. How weird it looked!

NGC 1365 in visible and infrared light. Credit: ESO/P. Grosbøl

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But really, as today's APOD shows us, the arms of NGC 1365 curve back gracefully, so that they almost seem to form a full disk of NGC 1365. It is the arms of another galaxy, NGC 6872, that seem to "reach for infinity"!

Long-armed galaxy NGC 6872. Credit: ESO/VLT, Judy Schmidt

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NGC 1365 is sort of lurking on the outskirts of the Fornax Cluster, which otherwise is heavily dominated by elliptical galaxies:

The Fornax Cluster of Galaxies. NGC 1365 is prominent at lower right. Credit: ESO. Acknowledgement: Aniello Grado and Luca Limatola

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I chose this ESO image over the beautiful APOD from January 29, 2022 that today's caption links to, because the APOD is too large for me to post without bystander being angry with me. But I do recommend the APOD, because in that picture you can easily tell the difference between stars and galaxies.

In any case, it certainly to be expected that NGC 1365 wouldn't dwell in the center of a group of large ellipticals. In large galaxy groups, galaxies constantly interact and chaff against each other, destroying dust lanes and driving gas out of one another, and the large central giant will (at least occasionally) zap the other galaxies with a jet from its black hole (and, even if it misses, it will heat up the intergalactic medium and make everything turbulent around it).

This artist's impression of 3C321 shows the main galaxy and the companion galaxy. A jet of particles generated by a supermassive black hole at the center of the main galaxy is striking the companion galaxy. The jet is disrupted and deflected by this impact. (Credit: Illustration: NASA/CXC/M. Weiss)

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As a result of all the bullying near the center of a galaxy cluster, practically all the galaxies there will end up as yellow blobs. The elegant spiral galaxies that belong to galaxy clusters will almost always be found well away from the center. Take a look at the picture below of an (annotated but blurry) wide field chart of the Virgo Cluster. The center of the Virgo Cluster is at bottom left, and giant elliptical monster M87 is actually off the chart. At lower left, circled in yellow, you can see another large elliptical galaxy, M86, and at upper center, you can see large spiral M100 that is a good distance away from the cluster center:

Annotated wide field view of a part of the Virgo Cluster. The cluster center
is at lower left. M86, circled in yellow, is close to the cluster center,
while M100, circled in blue, is much farther way from it. Credit: NASA, ESA, DSS 2

So what do M86 and M100 look like?

M86, near the center of the Virgo Cluster. Credit: NOIRLAB/NSF/AURA

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M100, quite far from the center of the Virgo Cluster. Credit: ESO

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As you can see, the conditions near the center of a galaxy cluster are not conducive to the formation of elegant spiral arms with dust lanes and young blue clusters and pink nebulas!

And a small blue galaxy falling into the Fornax cluster will soon be aware of this! Both in the APOD from January 2022 and in the ESO image, you can see this little blue whiff of a thing at about 9 o'clock. That is NGC 1427A, and it is a hapless dwarf galaxy helplessly falling into the Fornax Cluster.

Galaxy NGC 1427A will not survive long as it is falling helplessly 'up' into the Fornax Cluster. It is undergoing a violent burst of star formation as it is falling in. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

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Let's look a little bit more at the inner workings of NGC 1365. This is what the central part of NGC 1365 looks like to JWST:

Webb’s image of galaxy NGC 1365 shows a central region that looks like an angled, smashed oval that is a mix of bright orange shades that emanate a blue glow. The galaxy’s bar extends horizontally from the oval. It is crossed by messy dust filaments that curve slightly, forming a backward S shape. Fainter filaments appear below and above the core. Credit: NASA, ESA, CSA, STScI, J. Lee (STScI), T. Williams (Oxford), PHANGS Team

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This is how the center of NGC 1365 works:

Optical image of NGC 1365 from the Dark Energy Survey (left)
and schematics illustrating the structures within the central galactic bar (right).
Credit: Schinnerer et al. 2023

JWST + Hubble image of the center of NGC 1365.
Note the gas flowing into the center along the dust lanes.

Gas is flowing into the center of NGC 1365, leading to massive star formation there. I'm thinking of nearby galaxy M82. So much of the gas of M82 has flowed into the center of this galaxy that star formation has stopped in the disk. But there is so much star formation in the center that ionized gas is being violently expelled from the center of M82.

Messier 82. Composite of Chandra, HST and Spitzer images. X-ray data recorded by Chandra appears in blue; infrared light recorded by Spitzer appears in red; Hubble's observations of hydrogen emission appear in orange, and the bluest visible light appears in yellow-green. Credit: NASA/JPL-Caltech/STScI/CXC/UofA/ESA/AURA/JHU

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The reason for the concentration of gas in the center of M82 is the interaction between M81, M82 and NGC 3077.

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Gas streams between M81, M82 and NGC 3077. Credit: Kevin V. Croxall et al.

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NGC 3077 is also part of the action. And even more than M82, it has lost its gas almost everywhere except in its enter. And just like M82, NGC 3077 is sporting a brilliant burst of star formation in its center.

NGC 3077, a yellow blob of faint old stars with a brilliant burst of star formation in its center. Credit: ESA/Hubble & NASA

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Ann

[Jean-Baptiste Auroux]

Thanks Ann, very intersting post !!
CS,
JB

[Christian G.]

Majestic galaxy indeed! Beautiful image too. And holy smokes, the central black hole link mentions that this one is spinning almost at the speed of light, is that common among SMBHs? There are some pretty wild things in heaven and earth, Horatio…

[VictorBorun]

This is how the center of NGC 1365 works:

Optical image of NGC 1365 from the Dark Energy Survey (left).
Credit: Schinnerer et al. 2023
Ann

so a bar in a barred galaxy is a pair of wide and slightly curved jets flowing to the ring-shaped core if the ring happens to be at large angle to the galactic plane?

is it because the ring has orbital electric current and sustains a torus of magnetic field that is blocking ionised interstellar gas from coming in in the plane of the ring?

[Ann]

This is how the center of NGC 1365 works:

Optical image of NGC 1365 from the Dark Energy Survey (left).
Credit: Schinnerer et al. 2023
Ann

so a bar in a barred galaxy is a pair of wide and slightly curved jets flowing to the ring-shaped core if the ring happens to be at large angle to the galactic plane?

is it because the ring has orbital electric current and sustains a torus of magnetic field that is blocking ionised interstellar gas from coming in in the plane of the ring?

The bar is not just a pair of dust lanes leading gas into a typically ring-shaped core. A bar is also a collection of stars, usually but not always old yellow stars, that form a sort of "crossbar" over the galactic core.

A perfect example of a bar with a pair of dust lanes and a ring surrounding the nucleus is NGC 1300:

NGC 1300 is the 'other' iconic barred galaxy (NGC 1365 is either the first or the second one). The two dust lanes leading gas into the center of NGC 1300 are not strikingly visible in this image, but you can see them, Credit: NASA, ESA, and The Hubble Heritage Team STScI/AURA

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Infrared view of the bar of NGC 1300 by JWST's MIRI instrument. Credit: Judy Schmidt.

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Another galaxy that sports both a pair of dust lanes and a central ring (plus an outer ring, too) is M95:

This image of spiral galaxy NGC 3351 (M95) combines observations from several observatories to reveal details about its stars and gas. Radio observations from the Atacama Large Millimeter/submillimeter Array (ALMA) show dense molecular gas in magenta. The Very Large Telescope’s Multi Unit Spectroscopic Explorer (MUSE) instrument highlights where young massive stars illuminate their surroundings, set off in red. The Hubble Space Telescope’s images highlight dust lanes in white and newly formed stars in blue. High-resolution infrared images from the Webb Space Telescope will help researchers identify where stars are forming behind dust and study the earliest stages of star formation in this galaxy. Credit: SCIENCE: NASA, ESA, ESO-Chile, ALMA, NAOJ, NRAO IMAGE PROCESSING: Joseph DePasquale (STScI)

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Another interesting barred galaxy is NGC 7496. I can't really spot a ring around the core in this JWST image, but the dust lanes of the bar are plain to see:

NGC 7496. Credit: JWST/Judy Schmidt

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A galaxy that doesn't immediately look barred, but which has the dust lanes typical of bars, is M100:

M100. Note the two prominent dust lanes that wind their way almost all the way into the core. There is a bright ring around the core, too. Credit: Hubble Legacy Archive, NASA, ESA - Processing & Licence: Judy Schmidt

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A barred galaxy that certainly doesn't lack a ring (make that rings), but seems to lack dust lanes in its bar, is NGC 1398:

Spiral galaxy NGC 1398 not only has a ring of pearly stars, gas and dust around its center, but a bar of stars and gas across its center, and spiral arms that appear like ribbons farther out. Image Credit: Mark Hanson; Data: Mike Selby

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NGC 1398 has a short yellow bar which appears to be made almost entirely of old yellow stars. Thin dust lanes appear to cut across the bar, but no dust lanes along the bar are visible.


Normally galactic bars are yellow, because their stellar populations are yellow and old. But not always. We do see galaxies that sport bright young clusters of blue stars in their bars:

The bar of galaxy NGC 7741 contains stars that are bright and blue. Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona

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We can see dust lanes that cut across the bar of NGC 7741, but no dust lanes that follow along the bar.


As for the Large Magellanic Cloud, it is a very obviously barred galaxy, but the bar is much more visible in optical light than in the infrared:

The Large Magellanic Cloud. Credit: Eckhard Slawik.

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The Large Magellanic Cloud in infrared light. Credit: Spitzer Space Telescope.

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What sets the Large Magellanic Cloud apart from many other galaxies is that it doesn't have a core. Therefore it doesn't have dust lanes feeding the core, and it doesn't have a ring of gas and dust orbiting the core.

A barred galaxy that used to have prominent dust lanes in its bar and a ring around its core is NGC 936. Star formation has long since ceased in this galaxy and its dust has dispersed, leaving only a ghostly bar-ring shape in its all-yellow population.

NGC 936. Credit: Sloan Digital Sky Survey.

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[shaileshs]

"NGC 1365's prominent bar plays a crucial role" .. Sorry, but where is the "bar" ? I zoomed and zoomed.. maybe I am challenged to see shapes OR people who think there's a bar are falling to brain's "looking for shapes and patterns" bias/tendency ?

[Ann]

"NGC 1365's prominent bar plays a crucial role" .. Sorry, but where is the "bar" ? I zoomed and zoomed.. maybe I am challenged to see shapes OR people who think there's a bar are falling to brain's "looking for shapes and patterns" bias/tendency ?

Ann

[AVAO]

"NGC 1365's prominent bar plays a crucial role" .. Sorry, but where is the "bar" ? I zoomed and zoomed.. maybe I am challenged to see shapes OR people who think there's a bar are falling to brain's "looking for shapes and patterns" bias/tendency ?

APOD 1 February 2024 annotated.png

Ann

"The two bars of NGC 1365 are a rare phenomenon and are thought to have originated by the combined effects of galaxy rotation and the complex dynamics of the stars. Its largest bar of stars, too large for its structure to be visible in this image, connects its outer spiral arms to its centre. What we can see is the much smaller second bar of stars, nestled within the main bar. It is likely this secondary bar acts independently of the main bar, rotating more rapidly than the rest of the galaxy." https://www.eso.org/public/images/potw2034a/




1. 2 or 3. It's all a question of wavelength. In the IR, the poor black hole in the middle even feels a bit left alone

Click to view full size image

jac berne (flickr)

[Ann]

"NGC 1365's prominent bar plays a crucial role" .. Sorry, but where is the "bar" ? I zoomed and zoomed.. maybe I am challenged to see shapes OR people who think there's a bar are falling to brain's "looking for shapes and patterns" bias/tendency ?

APOD 1 February 2024 annotated.png

Ann

"The two bars of NGC 1365 are a rare phenomenon and are thought to have originated by the combined effects of galaxy rotation and the complex dynamics of the stars. Its largest bar of stars, too large for its structure to be visible in this image, connects its outer spiral arms to its centre. What we can see is the much smaller second bar of stars, nestled within the main bar. It is likely this secondary bar acts independently of the main bar, rotating more rapidly than the rest of the galaxy." https://www.eso.org/public/images/potw2034a/




1. 2 or 3. It's all a question of wavelength. In the IR, the poor black hole in the middle even feels a bit left alone

Click to view full size image

jac berne (flickr)

You're right, Jac.

The two bars of NGC 1365 are extra visible in this infrared image by ESO:

NGC 1365 in infrared by ESO.

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The two bars in NGC 1365, marked in yellow.

Ann

[johnnydeep]

What's the angular extent of this galaxy compared to the Moon? I'm getting confused by the units. The Moon is 0.5° (degrees) in diameter. The Astrobin link shows this FOV:

If I'm reading this right, each box is 4 minutes squared, or 1/15 degrees squared. And 0.5° = 30 minutes, which means the Moon would be 7.5 boxes high and wide?

[VictorBorun]

This is how the center of NGC 1365 works:

Optical image of NGC 1365 from the Dark Energy Survey (left).
Credit: Schinnerer et al. 2023
Ann

so a bar in a barred galaxy is a pair of wide and slightly curved jets flowing to the ring-shaped core if the ring happens to be at large angle to the galactic plane?

is it because the ring has orbital electric current and sustains a torus of magnetic field that is blocking ionised interstellar gas from coming in in the plane of the ring?

The bar is not just a pair of dust lanes leading gas into a typically ring-shaped core. A bar is also a collection of stars, usually but not always old yellow stars, that form a sort of "crossbar" over the galactic core.

sigh
A bar as a star-populated part of the galaxy can not possibly be governed by a magnetic field even if a strong galactic magnet was there.

By the way after second glance at the diagram I can see that the bar is interpreted as an ellipse or a ring observed almost edge-on.
So there are two rings, posing as bars, in their different planes, and there is a pair of gas-dust streams from the outer bar/ring to the inner bar/ring and next to the very central region feeding the supermassive black hole.

The area where the magnetic field of the BB's accretion disk rules is far too small to see here…

[johnnydeep]

so a bar in a barred galaxy is a pair of wide and slightly curved jets flowing to the ring-shaped core if the ring happens to be at large angle to the galactic plane?

is it because the ring has orbital electric current and sustains a torus of magnetic field that is blocking ionised interstellar gas from coming in in the plane of the ring?

The bar is not just a pair of dust lanes leading gas into a typically ring-shaped core. A bar is also a collection of stars, usually but not always old yellow stars, that form a sort of "crossbar" over the galactic core.

sigh
A bar as a star-populated part of the galaxy can not possibly be governed by a magnetic field even if a strong galactic magnet was there.

By the way after second glance at the diagram I can see that the bar is interpreted as an ellipse or a ring observed almost edge-on.
So there are two rings, posing as bars, in their different planes, and there is a pair of gas-dust streams from the outer bar/ring to the inner bar/ring and next to the very central region feeding the supermassive black hole.

The area where the magnetic field of the BB's accretion disk rules is far too small to see here…

Chiming in here where I probably shouldn't be, and putting my Chris Peterson hat on, I'd think that any galaxy-wide magnetic fields (if there even are any) would be too weak to affect either the bar or the rest of the galaxy.

[Chris Peterson]

The bar is not just a pair of dust lanes leading gas into a typically ring-shaped core. A bar is also a collection of stars, usually but not always old yellow stars, that form a sort of "crossbar" over the galactic core.

sigh
A bar as a star-populated part of the galaxy can not possibly be governed by a magnetic field even if a strong galactic magnet was there.

By the way after second glance at the diagram I can see that the bar is interpreted as an ellipse or a ring observed almost edge-on.
So there are two rings, posing as bars, in their different planes, and there is a pair of gas-dust streams from the outer bar/ring to the inner bar/ring and next to the very central region feeding the supermassive black hole.

The area where the magnetic field of the BB's accretion disk rules is far too small to see here…

Chiming in here where I probably shouldn't be, and putting my Chris Peterson hat on, I'd think that any galaxy-wide magnetic fields (if there even are any) would be too weak to affect either the bar or the rest of the galaxy.

I want my hat back!

I don't think I've ever seen anything to suggest that electrical or magnetic fields at galactic scales can do more than subtly shape gas and dust flows. They don't define where stars and resonance structures like bars and arms are. Those things are all driven by gravity.

[johnnydeep]

sigh
A bar as a star-populated part of the galaxy can not possibly be governed by a magnetic field even if a strong galactic magnet was there.

By the way after second glance at the diagram I can see that the bar is interpreted as an ellipse or a ring observed almost edge-on.
So there are two rings, posing as bars, in their different planes, and there is a pair of gas-dust streams from the outer bar/ring to the inner bar/ring and next to the very central region feeding the supermassive black hole.

The area where the magnetic field of the BB's accretion disk rules is far too small to see here…

Chiming in here where I probably shouldn't be, and putting my Chris Peterson hat on, I'd think that any galaxy-wide magnetic fields (if there even are any) would be too weak to affect either the bar or the rest of the galaxy.

I want my hat back!

I don't think I've ever seen anything to suggest that electrical or magnetic fields at galactic scales can do more than subtly shape gas and dust flows. They don't define where stars and resonance structures like bars and arms are. Those things are all driven by gravity.

Hat relinquished. Thanks for weighing in!

[Ann]

The way my math-challenged, blue-tinted brain understands it, the bar moves almost like a solid object, and it moves very differently than the arms. I guess that the chafing(?) motions at the bar-arm interface would have a big effect on the galaxy as a whole.

Milky Way spiral arms and bar resonances revealed by Gaia DR 2. Two exemplary new artist's views of a Milky Way spiral galaxy including the four-arm tightly-wound spiral arms revealed by Gaia DR 2. Modified images of original Milky Way galaxy rendering by Robert Hurt and Nick Risinger.

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More important still might be the way that the bar, specifically the dust lanes in the bar, feed gas into the central black hole of a barred galaxy.

Ann

[Chris Peterson]

More important still might be the way that the bar, specifically the dust lanes in the bar, feed gas into the central black hole of a barred galaxy.

By what mechanism? Is the dust and gas in the bar so dense it behaves like a viscous liquid, resulting in particles losing energy and spiraling inward? That wouldn't seem the case if all the particles in the bar are moving largely together. There shouldn't be frictional losses in that case.

Do barred galaxies generally have more active black holes than unbarred ones?

[Ann]

More important still might be the way that the bar, specifically the dust lanes in the bar, feed gas into the central black hole of a barred galaxy.

By what mechanism? Is the dust and gas in the bar so dense it behaves like a viscous liquid, resulting in particles losing energy and spiraling inward? That wouldn't seem the case if all the particles in the bar are moving largely together. There shouldn't be frictional losses in that case.

Do barred galaxies generally have more active black holes than unbarred ones?

I have no idea, of course. But this illustration of the bar of NGC 1365 does show the motion of the bar to be "inward", towards the core and the black hole:

https://www.researchgate.net/figure/An- ... _368584574

Ann

[VictorBorun]

More important still might be the way that the bar, specifically the dust lanes in the bar, feed gas into the central black hole of a barred galaxy.

By what mechanism? Is the dust and gas in the bar so dense it behaves like a viscous liquid, resulting in particles losing energy and spiraling inward? That wouldn't seem the case if all the particles in the bar are moving largely together. There shouldn't be frictional losses in that case.

Do barred galaxies generally have more active black holes than unbarred ones?

A galactic disk of gas hardly has any friction from its differential rotation and starve the central black hole.
But its majesty NGC 1365 has two rings (posing as bars) in their different planes and so the friction is larger. Is it?

[Chris Peterson]

More important still might be the way that the bar, specifically the dust lanes in the bar, feed gas into the central black hole of a barred galaxy.

By what mechanism? Is the dust and gas in the bar so dense it behaves like a viscous liquid, resulting in particles losing energy and spiraling inward? That wouldn't seem the case if all the particles in the bar are moving largely together. There shouldn't be frictional losses in that case.

Do barred galaxies generally have more active black holes than unbarred ones?

A galactic disk of gas hardly has any friction from its differential rotation and starve the central black hole.
But its majesty NGC 1365 has two rings (posing as bars) in their different planes and so the friction is larger. Is it?

Larger? Probably. Large enough to steal enough energy to result in significant transfer of material to the center? I don't know. I'd think that the densest regions we see here are still hard vacuums with stars far apart.