ARP GALAXIES

[Martin Meredith]

I was looking at the supernova in NGC 514 a couple of nights back and noticed not one but 3 Arps nearby. They fit comfortably into a single shot even with the Lodestar at 800mm focal length. 

Arp 48 is classed as a spiral with a low surface brightness companion on its arm. The negative shots are zooms with N up. The stellar-looking object to the SE of the spiral is a galaxy, as is the slightly fainter object to the W. It isn't clear which is the LSB companion noted by Arp. The other blobs in the image appear to be very faint galaxies in a cluster. The DSS image shows a tail starting at the W edge and curving tightly back on itself. I've a hint of it here, but no more.

Arp 88 is very small and quite faint. It is (strangely?) classified as a spiral with a large high surface brightness companion on its arm (presumably the object to the W in this figure). One does wonder if Arp's descriptions for 48 and 88 are the wrong way round.

Of the three Arps, the showpiece is Arp 119. This is a member of the class of ellipticals with close perturbing spirals. The lower galaxy (UGC 849) is of type Sd and contains an active galactic nucleus (Markarian 984). We can just see the hints of multiple arms to the lower part. It seems clear that it has undergone (or is undergoing) an interaction, with all the tails fanned out behind it. The DSS image is well worth a look! I may revisit this is colour as there is a clear contrast between the two galaxies.

I also managed a look at the very fine ring galaxy Arp 146 in Cetus which I'll post separately.

Thanks for looking

Martin

 

Edited October 20, 2020 by Martin Meredith

[Mike JW]

Lovely when you can capture 3 Arps in one shot.

High resolution images seem to show obvious small, bright companions on the arm for 48 and 88. I think you have captured them but a longer focal length set up might make them more obvious.

http://cseligman.com/text/atlas/pgc04a.htm#pgc4789 - worth  a look at this link for Arp 48.

Mike

Edited October 21, 2020 by Mike JW
more info

[Martin Meredith]

Thanks for that link, Mike. They are indeed great descriptions and images.

Indeed, it seems that the companion Arp had in mind for Arp 48 is the closest dot to the E of the core of the main galaxy. The companion of the main galaxy in Arp 88 is a real challenge (the galaxy itself is mag 17. I have something in the right place (to the W) but no obvious structure. 

I'm not sure if this has already been mentioned earlier in the thread but the original Atlas of Peculiar Galaxies can also be downloaded as a single pdf here:

http://articles.adsabs.harvard.edu/pdf/1966ApJS...14....1A

which is quite convenient except that the images need to be rotated. 

Martin

[Martin Meredith]

One of my favourite types of Arp galaxies are the ring structures. Unfortunately there are only three to savour: Arps 146, 147 and 148, the first two in Cetus and the latter in Ursa Major. (There will be more out there to find outside the Arp catalogue...)

This is Arp 146. The full field shot shows how tiny this configuration appears. (There was a whole raft of satellites flying through here; choosing the outlier removal to retain 90% of pixels at each point got rid of most of them but I see that one managed to escape...).

What we have to put up with! This is using mean stacking with no outlier rejection:

Zoomed in a lot the ring becomes more apparent. The ring part is PGC 509 while the galaxy just below and to the left is PGC 510. It is thought that one galaxy passed through the other, leading to a bright ring of star formation. There is an excellent picture here: http://cseligman.com/text/atlas/pgc00a.htm showing how blue the ring is. One a good night I'd like to capture some colour for this pair. Apparently the pair is about a billion light years distant.

The challenge for all 3 ring galaxies is to capture as much of the ring as possible. I'm missing some compared to deeper shots. I will have to be more patient and wait for this object to transit on a night of good seeing!

Martin

 

[Mike JW]

Hi Martin - the cseligman site is a favourite of mine. Satellites!!!! - progress at any price I suggest. I still await a clear spell - more rain. Mike

[Mike JW]

22/10/20 - ARP 200 in Aries.

Arp classified this galaxy as 'not S or E with material ejected from the nucleus'. To me it looks like a spiral (disrupted) with a small bar? Officially classified as Sb.

Off to the left is a sneaky little galaxy hiding behind the pair of stars - Leda 1420905, mag 16.3. To the right is VV 606, which is two galaxies muddled up - mag 16 and classes as an irregular.

Arp spotted a faint plume heading off from the top end and going right-ish. I picked up (just) a star forming region (detached bit of grey) on the right near the top which marks where the plume should be. Really need to re-vist this when conditions allow 10 sec subs.

The windy conditions meant I had to do 120, 3 sec subs to be able to use the best 42.

Mike

[Mike JW]

ARP 168 (M32) - 22/10/20

If it wasn't for my tour of the Arps I would have no idea that M32 was in his catalogue. So why did he include it? It has a counter tail - diffuse tidal stream because of its interaction with M31, so he classified it as not S or E with a counter-tail.  However it is classed as E2. I never even thought to look for a tail when I had a big Dob. No idea what size Dob would even reveal the tail.

First image below - the 'noise' above M 32 is of course not noise but M 31 stars. Look below M 32 and the grey fuzz could well be the counter-tail. 

Whilst the subs were coming in, I was looking up info re M32 when I came across info on the Andromeda Globular Clusters - there are three in this image. A wonderful bonus. See the next image with red lines indicating them.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Below is a close of two of the Andromeda Globular Clusters

 

A really worthwhile observation and much pleasure. I wonder how many more Andromeda Globulars I could locate?

Mike

[Martin Meredith]

This is a new one to me (Arp 200). You did really well in challenging conditions to capture some good details, esp. with 3s exposures. The loop at the upper right is very evident.

Here it was very windy (~125km/h) earlier in the week -- a litle too much even for EEVA!

Martin

Edited October 23, 2020 by Martin Meredith

[Martin Meredith]

By coincidence, I was also looking at Arp 168 a few nights back, wondering about its inclusion in the Arp catalogue. What I found striking were what I imagine must be dusty regions of M31 -- only visible when stretched a lot. There is something that could be described as a plume (on the NE side of the galaxy in this shot), but equally it could be part of the outer envelope of M31.

Thanks for pointing out the globs of M31 (I now plan to add them as a catalogue). I can imagine how much fun it would be to track them all down.

Martin

 

 

 

 

[Mike JW]

Martin - agree distinguishing plume from outer regions of M31 is nigh on impossible? but see https://images.mantrapskies.com/catalog/ARP-GALAXIES/ARP168-M032/ARP168M32L4X10RGB4X10X3ID.jpg 

Mike

[Martin Meredith]

That's a great image. This is my LRGB version stretched as far as I can go, oriented almost like Rick's. Seems a case where we need AP amounts of data to see this plume! There are several quite bright globs in here according to his image, inlcuding the pinky-red object at the upper-right.

 

 

[Mike JW]

Much to learn and observe in M31 - hours of pleasure on just this one DSO.

Mike

[Bill S]

Over the past few night I had a good look at quite a few of the Arps mentioned recently in this thread. Arp 200 very impressive as others have shown.

 

 

Arp 276 is a good example of a pair of interacting galaxies.

 

 

And Arp 31 is a good example of an integral sign shaped galaxy. I took a fair number of subs and a lot of stretch + inversion helps show this clearly.

 

 

It's nice to see an Arp that is not too dim or small. M77 is also Arp 37 and is 'only' 35 to 47 million light years away. (Estimates seem to vary.)

 

 

Arps 113, 65, 295 are also fascinating sights.

 

 

 

 

[Mike JW]

A good haul of Arps, showing the variety of galaxies in the Arp catalogue. Mike

[callump]

Here is ARP 282 from last night. Comprising NGC 169 and IC 1559. Also in field NGC 160 to right, and UGC 354 above.

Not great sky conditions in that area of the sky for me last night. 

Callum

 

[Mike JW]

Hoping to re-visit this Arp some time soon. Weather and now moon not helping. Mike

[Mike JW]

ARP 98 in Triangulum, is not one to write home about. It is classified as 'Spiral with elliptical companion on its arm'. Last time I visited this interacting pair I used the C11 and struggled to see much, so last night I pointed the 15 at it. At mag 15 it certainly is a challenge and despite stacking for over 6 minutes there is not a wealth of detail on show. The main galaxy is classed as Sbc and the companion lies at the end of a 170,000 lyr bridge of stars. The pair lie somewhere in the region of 550 million lyrs away (figures vary).

Mike

 

[Martin Meredith]

When I observed this last December I too struggled to see much but with time a very interesting 'hook' shape (upside down question mark) emerged:

There appears to be a galaxy being obscured by the brightish star to the S though nothing is listed on my charts.

I certainly need smaller pixels to handle these horrible square stars!

Martin

 

[Mike JW]

Hi Martin,

The suspect galaxy near the star - NED gives it as an Infra-red source which I assume is therefore a galaxy?

As to smaller pixels - Ultrastar?

Mike

[Bill S]

Another look at Arp 98 from a few weeks ago when I was rambling around Triangulum. Seven minutes worth again although you could see the hook etc. after a couple of minutes worth of 15 second subs.

 

All good fun.

Bill

[Mike JW]

As you say, all good fun.

I think top right, the fuzz ball is PGC 5784 - mag 16 ish. Up and to the laft a bit is Leda 1980192 - 16.9 ish.

Mike

[Mike JW]

On October 27 Callum posted Arp 282 to which I replied I hoped to re-visit. From the pair head towards 5 o clock and you pass a faint fuzz (mag 18) - also on Callum's shot. There are two other fuzz spots (mag 17 galaxies).

Also in Callum's shot was NGC 160 and what a lovely sight that  is - classed as SO-a, with UGC 354 (NGC 162) above the bright star and Leda 212552 below NGC 160 (almost mag 17)

 

Mike

[Martin Meredith]

Here's a recent observation of Arp 282 to throw into the mix. I added about 1 minute in each of RGB to a 2 minute luminosity 'base' as I am starting to do when I see possibly interesting stars in the field.

I just noticed that the bright star at the right is a double (you can make out the secondary in line with the spikes to the SW). It is known as HO 623 (not sure who HO was). The primary is spectral type K2III and mag 7.2 while the secondary is just over 9 arcsecs away and has a magnitude of 12.3. It is separated in all three of our shots.

I love the delicate wound-up arms of the spiral NGC 160

[Mike JW]

1 hour ago, Martin Meredith said:

Here's a recent observation of Arp 282 to throw into the mix. I added about 1 minute in each of RGB to a 2 minute luminosity 'base' as I am starting to do when I see possibly interesting stars in the field.

I just noticed that the bright star at the right is a double (you can make out the secondary in line with the spikes to the SW). It is known as HO 623 (not sure who HO was). The primary is spectral type K2III and mag 7.2 while the secondary is just over 9 arcsecs away and has a magnitude of 12.3. It is separated in all three of our shots.

I love the delicate wound-up arms of the spiral NGC 160

 

HO = G. W. Hough. I had not thought to check out the double - nice one Martin. (I use to observe doubles but this one was not on my lists as the companion B was just out of reach of my scope.) Thanks for your post on Arp 282. Mike

[roelb]

Arp 282 with Evolution 8 @ f/5 and ZWO ASI290MM

6 x 10 s