APOD: Twin Galaxies in Virgo (2019 Feb 01)

[APOD Robot]

Twin Galaxies in Virgo

Explanation: Spiral galaxy pair NGC 4567 and NGC 4568 share this sharp cosmic vista with lonely elliptical galaxy NGC 4564. All are members of the large Virgo Galaxy Cluster. With their classic spiral arms, dust lanes, and star clusters, the eye-catching spiral pair is also known as the Butterfly Galaxies or the Siamese Twins. Very close together, the galaxy twins don't seem to be too distorted by gravitational tides. Their giant molecular clouds are known to be colliding though and are likely fueling the formation of massive star clusters. The galaxy twins are about 52 million light-years distant, while their bright cores appear separated by about 20,000 light-years. Of course, the spiky foreground stars lie within our own Milky Way.

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[Boomer12k]

Very nice... are there any images that show star trails?

:---[===] *

[Ann]

This is a fascinating and irritating pair. How can it be that they show no tidal distortions when they are practically on top of one another?

I found a great set of three different pictures comparing the appearance of these "Twin Galaxies" in Virgo. I can't post it here, because it is too large, 1.1 MB. I'm posting it here as a link anyway, but be warned: Don't open it if your computer, laptop or mobile can't handle that many bites.

http://zooniverse-resources.s3.amazonaw ... 7-4568.png

The 1.1 MB picture collection can be found on this page, which I recommend, if you want to see some more fascinating interacting galaxies.

Anyway. NGC 4567 and 4568 are two calm and sedate-looking spiral galaxies of unremarkable colors sitting right on top of one another doing nothing in particular. Don't tell me they are forming a lot of stars! I must commend Johannes Schedler and the CHART32 Team for really teasing out some undeniable pink splotches in both galaxies, but particularly in NGC 4568, the flat-looking one, thereby proving that they do indeed form some stars.

Note that NGC 4567, the face-on one, has a large outer spiral disk where no star formation is taking place. Only the inner disk is blue from young stars. But there is no major ongoing star formation there at all. To me, NGC 4567 looks like a relatively gas-poor galaxy, possibly because it has lost much of its gas due to interaction with the hot intracluster medium of the Virgo Cluster. Perhaps NGC 4567 could be a poor cousin several times removed of spectacular gas-losing spiral D100 in the Coma Cluster?

Ann

[Ann]

Click to view full size image

NGC 3314. Photo:
NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration
and W. Keel (University of Alabama)

Now that I'm at it, I have to show you some possibly related, yet not related, galaxy pairs. I'm talking about overlapping, non-interacting galaxies. A famous one is NGC 3314. The overlapping galaxies are overlapping so perfectly that they can only be told apart by calling them NGC 3314 A and NGC 3314 B. But they are well separated and aren't interacting at all!

Hubble Heritage wrote:

NASA's Hubble Space Telescope shows a rare view of a pair of overlapping galaxies, called NGC 3314. The two galaxies look as if they are colliding, but they are actually separated by tens of millions of light-years, or about ten times the distance between our Milky Way and the neighboring Andromeda galaxy. The chance alignment of the two galaxies, as seen from Earth, gives a unique look at the silhouetted spiral arms in the closer face-on spiral, NGC 3314A.

The motion of the two galaxies indicates that they are both relatively undisturbed and that they are moving in markedly different directions. This indicates they are not on any collision course. NGC 3314A's warped shape is likely due to an encounter with another nearby galaxy, perhaps the large spiral galaxy NGC 3312 (located outside the Hubble image).

Click to view full size image

2MASX J00482185-2507365.
NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

Click to view full size image

AM 1316-241.
NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration,
and W. Keel (University of Alabama, Tuscaloosa)

Wikipedia wrote:

The 2MASX J00482185-2507365 occulting pair is a pair of overlapping spiral galaxies found in the vicinity of NGC 253, the Sculptor Galaxy. Both galaxies are more distant than NGC 253, with the background galaxy, 2MASX J00482185-2507365 (PGC 198197), lying at redshift z=0.06, about 800 million light-years from Earth, and the foreground galaxy lying between NGC 253 and the background galaxy (0.0008 < z < 0.06).[4]

This pair of galaxies illuminates the distribution of galactic dust beyond the visible arms of a spiral galaxy. The heretofore unexpected extent of dust beyond the starry limits of the arms shows new areas for extragalactic astronomical study. The dusty arms extend 6 times the radii of the starry arms of the galaxy, and are shown silhouetted in HST images against the central and core sections of the background galaxy.

Wikipedia wrote:

AM 1316-241 is the name given to a pair of overlapping galaxies photographed by the Hubble Space Telescope. Notable for the visible dust revealed by the back light from the more distant galaxy. Until recently, the extensive dust far outside the visible portion of a galaxy was not known to exist.

But, uh-oh, this last pair may indeed be interacting.

Can't win them all.

Ann

[Guest]

Don't open it if your computer, laptop or mobile can't handle that many bites.

Hi Ann,

Just so you know, a bite is something you take out of a sandwich. A byte is something that a computer uses. They sound the same but are spelled differently.

Also, I love the images that you posted.

[Ann]

Don't open it if your computer, laptop or mobile can't handle that many bites.

Hi Ann,

Just so you know, a bite is something you take out of a sandwich. A byte is something that a computer uses. They sound the same but are spelled differently.

Also, I love the images that you posted.

Thanks!

I thought the word looked strange when I wrote it. Thanks for setting me straight!

And thanks for praising the pictures I posted!

Ann

[orin stepanek]

For Ann; Is this what you wanted to show?

[Tara_Li]

One of the things I love about the really large pictures APOD posts is that you can often find interesting things in the background. For example - at about pixel 75,750, there's a sharp point of light surrounded by lots of fuzziness. It doesn't exactly look like the normal elliptical/spherical galaxy, since the core brightness is too sharp, so I'm guessing it's *maybe* a comet? Or maybe it's just a chance alignment of a star and an elliptical galaxy - I dunno. Kinda neat, though.

[orin stepanek]

The twin galaxies look like they may be conjoined!

[orin stepanek]

One of the things I love about the really large pictures APOD posts is that you can often find interesting things in the background. For example - at about pixel 75,750, there's a sharp point of light surrounded by lots of fuzziness. It doesn't exactly look like the normal elliptical/spherical galaxy, since the core brightness is too sharp, so I'm guessing it's *maybe* a comet? Or maybe it's just a chance alignment of a star and an elliptical galaxy - I dunno. Kinda neat, though.

There are several galaxies in today's APOD; you may be looking at one of them!

[Ann]

For Ann; Is this what you wanted to show?
NGC 4567-4568.png

Thanks, Orin! Yes, it is!

Ann

[Ann]

One of the things I love about the really large pictures APOD posts is that you can often find interesting things in the background. For example - at about pixel 75,750, there's a sharp point of light surrounded by lots of fuzziness. It doesn't exactly look like the normal elliptical/spherical galaxy, since the core brightness is too sharp, so I'm guessing it's *maybe* a comet? Or maybe it's just a chance alignment of a star and an elliptical galaxy - I dunno. Kinda neat, though.

I found that one strange, too.

I know that David Malin once described a spheroidal dwarf galaxy with a sharp central light point as a "nucleated dwarf". So maybe the weird object in today's APOD is one, too. But it doesn't really look like one. The faint halo looks too much like a ghostly gas cloud of some sort, not like a collection of stars. Admittedly though, the halo of the weird object is the same dull grey color as the outer arms of NGC 4567, which are certainly made up of old stars.

Ann

[rstevenson]

One of the things I love about the really large pictures APOD posts is that you can often find interesting things in the background. For example - at about pixel 75,750, there's a sharp point of light surrounded by lots of fuzziness. It doesn't exactly look like the normal elliptical/spherical galaxy, since the core brightness is too sharp, so I'm guessing it's *maybe* a comet? Or maybe it's just a chance alignment of a star and an elliptical galaxy - I dunno. Kinda neat, though.

I think this is the spot you're talking about. I screen captured this from a 500% blowup of the image, then increased the brightness and contrast to bring out a little more detail. Seems like it could be a distant elliptical galaxy.

Rob

[starsurfer]

This image would look so much better north up!

[starsurfer]

One of the things I love about the really large pictures APOD posts is that you can often find interesting things in the background. For example - at about pixel 75,750, there's a sharp point of light surrounded by lots of fuzziness. It doesn't exactly look like the normal elliptical/spherical galaxy, since the core brightness is too sharp, so I'm guessing it's *maybe* a comet? Or maybe it's just a chance alignment of a star and an elliptical galaxy - I dunno. Kinda neat, though.

I think this is the spot you're talking about. I screen captured this from a 500% blowup of the image, then increased the brightness and contrast to bring out a little more detail. Seems like it could be a distant elliptical galaxy.

detail.jpg
Rob

This is the low surface brightness dwarf galaxy PGC 42075. There seem to be a lot of these in Virgo. I guess this is what you get when all star formation ceases and all that is left are old stars.

[rstevenson]

One of the things I love about the really large pictures APOD posts is that you can often find interesting things in the background. For example - at about pixel 75,750, there's a sharp point of light surrounded by lots of fuzziness. It doesn't exactly look like the normal elliptical/spherical galaxy, since the core brightness is too sharp, so I'm guessing it's *maybe* a comet? Or maybe it's just a chance alignment of a star and an elliptical galaxy - I dunno. Kinda neat, though.

I think this is the spot you're talking about. I screen captured this from a 500% blowup of the image, then increased the brightness and contrast to bring out a little more detail. Seems like it could be a distant elliptical galaxy.

detail.jpg
Rob

This is the low surface brightness dwarf galaxy PGC 42075. There seem to be a lot of these in Virgo. I guess this is what you get when all star formation ceases and all that is left are old stars.

Thanks starsurfer. So being a dwarf galaxy closer than my hypothesized distant elliptical, I suppose that makes the bright core more reasonable. As well, I suppose that during a long exposure a pinpoint of bright light from the core gets washed over more pixels, creating this rather odd looking bright core. How am I doing at supposing?

Rob

[Ann]

One of the things I love about the really large pictures APOD posts is that you can often find interesting things in the background. For example - at about pixel 75,750, there's a sharp point of light surrounded by lots of fuzziness. It doesn't exactly look like the normal elliptical/spherical galaxy, since the core brightness is too sharp, so I'm guessing it's *maybe* a comet? Or maybe it's just a chance alignment of a star and an elliptical galaxy - I dunno. Kinda neat, though.

I think this is the spot you're talking about. I screen captured this from a 500% blowup of the image, then increased the brightness and contrast to bring out a little more detail. Seems like it could be a distant elliptical galaxy.

detail.jpg
Rob

This is the low surface brightness dwarf galaxy PGC 42075. There seem to be a lot of these in Virgo. I guess this is what you get when all star formation ceases and all that is left are old stars.

Thanks for identifying it, starsurfer.

Click to view full size image

NGC 3309, 3311, 3312. Source:
https://cgs.obs.carnegiescience.edu/CGS ... C3309.html

Rob, a distant (and therefore large and massive) elliptical galaxy wouldn't look like that. It wouldn't have such a bright concentrated center and such a diaphanous "body".

The picture at left shows galaxies just north of the twin galaxies in today's APOD. There are two massive elliptical galaxies there and a number of "anemic" spirals, which are losing their gas and their ability to form new stars.

As you can see, there is not a single galaxy here that looks like a bright point surrounded by a ghostly halo in remotely the same way as PGC 42075. Massive galaxies don't look like that, unless they are low surface brightness galaxies, like Malin 1.

Click to view full size image

Low Surface Brightness Galaxy Malin 1.
Photo: Gaspar Galaz et al., Megacam on the 6.5m Magellan/Clay telescope

No, I take that back. Even massive low-surface galaxies don't look like that.

Wikipedia wrote:

Malin 1 is a giant low surface brightness (LSB) spiral galaxy.[1][8] It is located 1.19 billion light-years (366 Mpc) away in the constellation Coma Berenices, near the North Galactic Pole. As of February 2015, it is arguably the largest known spiral galaxy, with an approximate diameter of 650,000 light-years (200,000 pc),[5][6][7] six and a half times the diameter of our Milky Way. It was discovered by astronomer David Malin in 1986 and is the first LSB galaxy verified to exist.[8][7][5] Its high surface brightness central spiral is 30,000 light-years (9,200 pc) across, with a bulge of 10,000 light-years (3,100 pc).[5] The central spiral is a SB0a type barred-spiral.

I guess PGC 42075 is a low surface brightness nucleated dwarf spheroidal galaxy after all.

Ann

Edit: Alcor just informed me that the NGC 3309/3311/3312 trio is nowhere near the overlapping twins in Virgo! Thanks, Alcor!

[sillyworm 2]

Malin 1..what an incredible structure !!! I would love to see a clearer view of the obviously wild 3D perameters.

[dlw]

There's an interesting object just to the right (2 o'clock) of NGC 4567. Looks like a very small spiral galaxy. Of course it might be very far in front or behind the Butterfly.

FWIW:

[Whoa!]

they are well separated and aren't interacting at all!

..yet

BTW - thanks, Ann, for the really excellent photo of NGC3314A & B! Absolutely magnificent!

[Ann]

There's an interesting object just to the right (2 o'clock) of NGC 4567. Looks like a very small spiral galaxy. Of course it might be very far in front or behind the Butterfly.

FWIW:

Interesting!

Click to view full size image

NGC 1232 with NGC 1232A at left. Photo: ESO.

Your object looks like a barred spiral galaxy to me. And since it is so small, I'd say it has to be pretty far in the background, because such miniature-sized spiral galaxies hardly exist - with perhaps one exception.

Alasdair Wilkins wrote:

Our Milky Way is just a spiral galaxy, but NGC 1232 here is a grand spiral galaxy, its diameter twice as long as ours. Everything is bigger in NGC 1232, including the giant satellite galaxy warping it out of shape.

So NGC 1232A is a tiny barred spiral galaxy, but it is a giant tiny barred spiral galaxy in view of its satellite kind!

The spiral galaxy you showed us near the twins NGC 4567/4568 doesn't look like it belongs to the twins at all. So it is almost certainly a background object.

Ann

[sillyworm 2]

http://cfht.hawaii.edu/en/news/Malin1/ I'm intrigued by the size of this galaxy! (Not sure how to make a link active here) Some interesting reading.

[starsurfer]

There's an interesting object just to the right (2 o'clock) of NGC 4567. Looks like a very small spiral galaxy. Of course it might be very far in front or behind the Butterfly.

FWIW:

Whatever this is, it isn't catalogued in either the SIMBAD or NED databases.

[Ann]

There's an interesting object just to the right (2 o'clock) of NGC 4567. Looks like a very small spiral galaxy. Of course it might be very far in front or behind the Butterfly.

FWIW:

Whatever this is, it isn't catalogued in either the SIMBAD or NED databases.

Is that where you found PGC 42075, starsurfer? How did you search for it?

Ann