20 replies to this topic

[Keith Rivich]

Perusing the "Atlas of the Messier Objects" (Stoyan et al) he mentioned that Halton Arp noticed (photographically I assume) a tail being drawn off of M32 and mingling in with one of the arms of M31. Thus his giving M32 the designation "Arp 168". In this most excellent image by Gendler,  http://www.robgendle...iggreyLRGB.html, the tail can clearly be seen extending from the north end of M32 and splitting a pair of 9th magnitude stars (SAO 36590 and PPM43235) slipping just past 14th magnitude GSC 02801-2033. The length of the tail, as measured in Megastar, is ~13' with a PA of 21deg. 

 

For some unknown reason I have never tried to see this visually. Anyone have luck with this?

 

Even worse I have observed the fairly easy 15th magnitude globular G213 which is right at the end of the tail. Go figure!

 

Same question for the apparent and very faint bridge connecting  M110 to M31, also seen in Gendlers image. 

Edited by Keith Rivich, 06 February 2018 - 11:49 PM.

[star drop]

The brighter splotch on M32's presumed tail closest to M32 is easily visible. I always thought that it was a brighter spot in M31's arm but that image sure suggests a tidal tail.

 

I can trace the edges of M31 to match the image and I also see a faint symmetrical twist to M110 on its outside edge pointing in the opposite direction of its bridge (in the image it would be the brightness drop off is offset more to the lower left of M110). The edge of M31 is not that difficult on a good night, much easier for me than the brightness variation across the dwarf galaxy Leo I.

 

That is one heck of a deep image! Thank you for sharing!

 

My observations are with a 25" f/5 at 88x magnification at a site where magnitude 6 stars are visible to good unaided eyes.

 

 

The seeing at my location is never very good, consequently I have never been able to pinpoint ANY of the globular clusters. Are any attainable with 88x?

[IVM]

Good stuff. Did see G213, did not know about the tail.

[Keith Rivich]

The brighter splotch on M32's presumed tail closest to M32 is easily visible. I always thought that it was a brighter spot in M31's arm but that image sure suggests a tidal tail.

 

I can trace the edges of M31 to match the image and I also see a faint symmetrical twist to M110 on its outside edge pointing in the opposite direction of its bridge (in the image it would be the brightness drop off is offset more to the lower left of M110). The edge of M31 is not that difficult on a good night, much easier for me than the brightness variation across the dwarf galaxy Leo I.

 

That is one heck of a deep image! Thank you for sharing!

 

My observations are with a 25" f/5 at 88x magnification at a site where magnitude 6 stars are visible to good unaided eyes.

 

 

The seeing at my location is never very good, consequently I have never been able to pinpoint ANY of the globular clusters. Are any attainable with 88x?

The short answer is yes though at such low power I.D. becomes an issue as M31 is a very busy galaxy. One would think you could bump up power, despite the seeing, to narrow down the field a bit. Even at high powers the globs are stellar.

[blb]

Perusing the "Atlas of the Messier Objects" (Stoyan et al) he mentioned that Halton Arp noticed (photographically I assume) a tail being drawn off of M32 and mingling in with one of the arms of M31. Thus his giving M32 the designation "Arp 168". In this most excellent image by Gendler,  http://www.robgendle...iggreyLRGB.html, the tail can clearly be seen extending from the north end of M32 and splitting a pair of 9th magnitude stars (SAO 36590 and PPM43235) slipping just past 14th magnitude GSC 02801-2033. The length of the tail, as measured in Megastar, is ~13' with a PA of 21deg. 

 

For some unknown reason I have never tried to see this visually. Anyone have luck with this?

 

Even worse I have observed the fairly easy 15th magnitude globular G213 which is right at the end of the tail. Go figure!

 

Same question for the apparent and very faint bridge connecting  M110 to M31, also seen in Gendlers image. 

Really? Can that be determined with only a photo? How do you know that it is not like the planetary nebula in M46? Or is it in front of the cluster/galaxy like planetary nebula NGC2438? Show me the paper or journal where this was published and I will believe it. I really do not think a photo, no mater how good it is, can prove what you are saying.

[Keith Rivich]

 

Perusing the "Atlas of the Messier Objects" (Stoyan et al) he mentioned that Halton Arp noticed (photographically I assume) a tail being drawn off of M32 and mingling in with one of the arms of M31. Thus his giving M32 the designation "Arp 168". In this most excellent image by Gendler,  http://www.robgendle...iggreyLRGB.html, the tail can clearly be seen extending from the north end of M32 and splitting a pair of 9th magnitude stars (SAO 36590 and PPM43235) slipping just past 14th magnitude GSC 02801-2033. The length of the tail, as measured in Megastar, is ~13' with a PA of 21deg. 

 

For some unknown reason I have never tried to see this visually. Anyone have luck with this?

 

Even worse I have observed the fairly easy 15th magnitude globular G213 which is right at the end of the tail. Go figure!

 

Same question for the apparent and very faint bridge connecting  M110 to M31, also seen in Gendlers image. 

Really? Can that be determined with only a photo? How do you know that it is not like the planetary nebula in M46? Or is it in front of the cluster/galaxy like planetary nebula NGC2438? Show me the paper or journal where this was published and I will believe it. I really do not think a photo, no mater how good it is, can prove what you are saying.

 

I am not suggesting any such proof.  I have not read any papers on the alleged tail but visually it meanders off M32 and mingles in with the outer arm of M31.  Whether a chance alignment or the real deal, it makes no matter. 

[IVM]

The Arp catalog is full of image interpretations that are (at least) questionable in the light of (at least) subsequently accumulated data. I think this particular enhancement may be related to the earlier passage of M32 through the disk but an area of enhanced star formation rather than a tidal tail per se. I need to look in the van den Bergh and Boyd monographs to remember what they say about it. Regardless it is an interesting feature to observe, and I haven't revisited this part of M31 in a long while.

[Keith Rivich]

Here ya go...

 

https://arxiv.org/pd...-ph/0111465.pdf

Edited by Keith Rivich, 07 February 2018 - 02:27 PM.

[GlennLeDrew]

In Gendler's image, M32 is too closely superimposed upon M31's disk to reveal a tidal tail for M32; I do see a spiral arm segment pretty sharply delineated. Broad-band optical imagery does not sufficiently differentiate the (expected) low surface brightness overdensity of old population II stars from the pretty bright disk structures of M31.

 

For M110, on the other hand, a tidal tail is quite clearly revealed.

[Keith Rivich]

In Gendler's image, M32 is too closely superimposed upon M31's disk to reveal a tidal tail for M32; I do see a spiral arm segment pretty sharply delineated. Broad-band optical imagery does not sufficiently differentiate the (expected) low surface brightness overdensity of old population II stars from the pretty bright disk structures of M31.

 

For M110, on the other hand, a tidal tail is quite clearly revealed.

I dunno. In the image there is clearly a line of bluish stars streaming down from M32 in the 4:00 direction which is nearly perpendicular to M31's spiral arm. M110's is more broad and diffuse.

[Starman1]

Try this super-deep image:

https://web.archive....m:80/M31B&W.htm

[Cotts]

Two people here have mentioned the tail from M110 in the Gendler image.  M110 isn't in the Gendler image...  Or am I having a senior moment?  What are you looking at?

 

Anyway I looked carefully at the Gendler image and the deeper one that Don linked and I cannot distinguish what might be emanating from M32 and what are the outer reaches of M31.  In Don's deep image the distortion and tails of M110 are obvious, by the way but I'm mostly concerned with the tail of M32...

 

The paper linked does show the M32/M31 tidal tail but only via isophotes captured with deep imaging with a biiiiig professional telescope, very expensive filters and sensors and with the light of M31 subtracted.  And still they are juuuuust there and are mostly revealed by statistical analysis of the isophotes....

 

Is someone with a class one human eyeball, an amateur-sized telescope and no ability to subtract the annoying light of M31 going to see it?  Or is the human brain making a pattern of random faint stars into a bridge?

 

Dave

[Starman1]

Dave,

Just scroll down--M110 (NGC205) is in the Gendler photo to the left of M31.

It's not surprising that a small satellite galaxy of M31 would be tidally distorted by M31, or that some mass might even be completely around its entire orbit.

We see that with the satellites of the Milky Way, for example.

So all you're really asking is if there is a VISIBLE bridge in images.  Probably not, though if we had information about all the star movements in the area, we'd

probably know it was there.

The Hallas image shows another interesting thing: the opposite ends of M31 are warped in opposite directions.

Cause by a satellite galaxy? If so, which?

[Cotts]

Senior moment.  More coffee.

 

Dave

[star drop]

In the Hallas image M110 looks a bit like a disrupted disk galaxy. I have seen two of the five? dark blotches visually.

[Starman1]

In the Hallas image M110 looks a bit like a disrupted disk galaxy. I have seen two of the five? dark blotches visually.

Yes.

In this image: https://freestarcharts.com/messier-110

it looks like its classification as a dwarf elliptical.

Except the center looks a little odd.

It's classified as an E5 peculiar, and often peculiar galaxies are thought to result from the collision of two or more smaller galaxies.

Does the Hallas photo (the deepest I've seen that does not burn it out) reveal it was a small disc galaxy colliding with an elliptical?

This ultra-violet image shows it as an elliptical with a compressed core:

 https://apod.nasa.go...aGalex_2048.jpg

This infrared image shows the core is spread out:

https://sep.yimg.com...da-galaxy-9.jpg

 

In the Hallas image, do I detect a shadow from its gas stream extending all the way to the nucleus of M31?

-------------------------------------------------------------------------

 

Good close-up of M32: https://www.universe...84594524605.jpg

Partially resolved: http://www.messier-o...2015/04/M32.jpg

NASA image, resolved: https://www.nasa.gov...s/image/m32.jpg

With nebulae!!: http://www.slate.com...al-original.jpg

Edited by Starman1, 09 February 2018 - 02:19 PM.

[GlennLeDrew]

The fact of the bluish color for the star 'stream' seeming to emanate from M32 is a clue; they're most assuredly M31's young disk stars, and cannot be related to the old, yellower (and generally dimmer) population of stars comprising M32.

[Keith Rivich]

The fact of the bluish color for the star 'stream' seeming to emanate from M32 is a clue; they're most assuredly M31's young disk stars, and cannot be related to the old, yellower (and generally dimmer) population of stars comprising M32.

 

 

But what if the interaction caused a burst of star formation? The fact that the stream does not align with M31's grain is a bit suspicious. Never-the-less...it looks like in interesting feature to try and observe.

Edited by Keith Rivich, 09 February 2018 - 07:25 PM.

[GlennLeDrew]

The nearly gas-free M32 (like M110) can trail essentially stars only; what gas there is is principally the very low density ''exhalations' of stellar winds. It would require *far* denser molecular cloud material to be stripped away, which upon colliding with gas in the cannibalizing galaxy would tend to lead to a rash of star formation. Stars in collision with gas can pretty much never initiate new star formation--at least not on the scale of a visibly *prominent* enhancement. A star is more of a repulsor of gas due to its stellar wind, not an attractor in the vein of a 'condensation nucleus.'

 

Both M32 and M110 have long since had their molecular gas content torn away via ram pressure stripping, as they circled about and through the mostly low-density (gas wise) halo of M31. (Local concentrations of molecular gas lofted into the halo from the active disk would present more robust structures by which to effect rapid, episodic stripping.)

Edited by GlennLeDrew, 10 February 2018 - 07:54 PM.

[GlennLeDrew]

When considering dwarf galaxies in relatively close orbit about a far larger galaxy, due attention must be given to the fact of warping of the still gravitationally bound structure, which can appear to be tidally stripped matter. In the case of M110, some portion of the extension that appears to continue on to a tidal tail will still be within the dwarf's tidal limit and so not yet be lost to the system. That is, M110's halo will be asymmetrically distorted. This is strongly supported by the lack of a similarly prominent 'tail' opposite to the one so easily seen. Pure tidal tails tend to be much more symmetrical, with the leading and trailing tails exhibiting relatively similar projected density and length.

 

On the matter of warping... The noted warp to M31's outer disk may not be due to M32/M110. To me these comparative lightweights (or even their formerly more massive incarnations?) don't seem much capable of raising such tides upon so massive a system. I wonder if an ancient (but not necessarily close) encounter between M31 and M33, or even our Milky Way, might be the causal factor. In such case, the disk warp would be expected to once have been more pronounced. Just a little theorizing on my part. It would be interesting to try to trace back in time potential trajectories of the member galaxies in the Local Group over the past 10 Gyr or so.

[Keith Rivich]

When considering dwarf galaxies in relatively close orbit about a far larger galaxy, due attention must be given to the fact of warping of the still gravitationally bound structure, which can appear to be tidally stripped matter. In the case of M110, some portion of the extension that appears to continue on to a tidal tail will still be within the dwarf's tidal limit and so not yet be lost to the system. That is, M110's halo will be asymmetrically distorted. This is strongly supported by the lack of a similarly prominent 'tail' opposite to the one so easily seen. Pure tidal tails tend to be much more symmetrical, with the leading and trailing tails exhibiting relatively similar projected density and length.

 

On the matter of warping... The noted warp to M31's outer disk may not be due to M32/M110. To me these comparative lightweights (or even their formerly more massive incarnations?) don't seem much capable of raising such tides upon so massive a system. I wonder if an ancient (but not necessarily close) encounter between M31 and M33, or even our Milky Way, might be the causal factor. In such case, the disk warp would be expected to once have been more pronounced. Just a little theorizing on my part. It would be interesting to try to trace back in time potential trajectories of the member galaxies in the Local Group over the past 10 Gyr or so.

This paper suggest that at ~z=1 outside (of the local group) galaxies dominated interactions. Perhaps an interaction occurred during this epoch.

 

Another paper, not refereed and invoking MOND, suggest that M31 and the Milky Way had an interaction early in their careers.