ARP GALAXIES

[Martin Meredith]

Here's my Arp 314 which doesn't add much. I've been exploring the effect of different stretches on this one. Hyper definitely helps bring out the contrast between the core regions of the galaxies and the surrounding parts. The fact that my exposure duration almost matches yours is a complete coincidence. I left it running to see if I could bring out some of the faint arms and also to catch the fainter fragment to the lower left of the galaxy pair.

 

This was one of 8 Arps I looked at last night out of a total of 33 objects over the course of a long 3h40m session, taking advantage of better-than-poor seeing, no moon, and a fortunately inaccurate cloud forecast!

Martin

[Martin Meredith]

Here's a packed galaxy field in Pisces displaying a great range of galaxy types as well as Arp 229 (to the lower right), all circling the mag 7.6 star HD 8347.

Arp 229 belongs in the 'concentric rings' category, this designation applying to the brighter of the pair, E-S0 type NGC 507. The fainter member is the elliptical NGC 508. They're also members of the overlapping galaxies catalogue due to the proximity of their outer halos.

The close-up of the lower part of the field also shows S0 type NGC 504 which is seen exactly edge-on (inclination 90 degrees) with a position angle of 45 degree, so somehow meets the Platonic ideal for galaxies... I'm trying and failing to visualise the cause of the curve in the rightmost spiral arms of this galaxy. Interaction? The distance estimate of 205 MLyrs is similar to NGC 494 but lower than most of the other galaxies in this field (~265-285 MLyrs).

NGC 494 is a type Sab with an 83 degree inclination that is just right to see the spiral arms.

The upper part contains 4 further NGC galaxies and a range of slightly fainter galaxies. NGC 501 is a compact elliptical while the bright NGC 499 is type E-S0. NGC 496 is Sbc although the structure is a bit fuzzy in this image. NGC 495 is the star here with the classic bar, type S0-a (bar). Again, the distance estimates cover a range from 210-260 MLyrs.

Martin

Edited October 9, 2021 by Martin Meredith

[Mike JW]

Hi Martin, 

It is still quite wonderful what a 8" scope will pick up.

I have been looking further into Arp 3, so I went back to the original data and like you fiddled with stretches and settings to try to tease out more detail.

Firstly Arp 3, is PGC 69293, classed as SA(s)m (in other words it is a magellanic dwarf type of galaxy) so no surprise it has a low surface brightness. It has a mag of 12.9. There seems to be disagreement as to its distance - possibly 64 million lyrs away but more likely 75-80 million llyrs away.

Labelled in the re processed shot below are three quasars and it would appear I just got a mag 20.9? at around 10.7 billion lyrs away - staggering thought and the mag 19.3 is even further away.

 

In the zoomed in shot below, the fuzz spots as indicated by the red lines are stars in our galaxy if I have interpreted high resolution images correctly. The remaining fuzz spots are therefore star clusters/formations in the actual galaxy.

Mike

[Mike JW]

Hi Martin, Your latest Arp and my comments on Arp 3 crossed somewhere in the ether.

Re ARP 229 - one of those inspiring views. I just sit there and enjoy the view as it appears on the screen. Here is my close up from a year a go. It is very much a case of a 'little and large' pairing. Your shot gives a hint of the concentric rings - mine does not. However using the same data, reducing the brightness and using log stretch the second shot gives a better hint of the concentric ring structure.

Mike

 

[Martin Meredith]

Its fascinating to revisit old captures to seek out new details. I definitely don't have the mag 20.9 quasar in my image although the other two are pretty bright. The last two nights I have been exploring distant quasars (z > 4) and managed to pick up a z = 4.26 at mag 20.1 and just possibly a 4.36 at mag 20.9 (right on the edge of detection). I'll post about those in a separate quasars thread!

What your last post illustrates is one of the main differences between EEVA and AP: interactivity. There are some stretch settings that bring out certain details but leave the rest of the field looking ugly, and others that lose the details but produce a cleaner overall appearance. We need both! The rings look very clear in your log stretch case.

That reminds me that I'd really like to implement a 'standard' stretch that can be applied to any image to enable comparisons. I'm thinking of something like the one used in the de Vaucouleurs Atlas of Galaxies which is essentially a log stretch from a photometrically-defined baseline (so the pixel values can be compared across images).

Martin

[Martin Meredith]

This thread is getting quite long now so I'm not sure if we've already seen this one...

Here are two Arps in Cetus for the price of one. Arp 133 is the elliptical just left and up from the centre. This is NGC 541. Arp classified it as 'Elliptical with nearby fragments' and one can see why. The faint companion at 9 oclock is a mag 17.2 galaxy and this, together with the rest, look like a superimposed but more distant galaxy chain.

However, the SDSS view on Aladin tells a different story. While the 9 oclock companion is clearly galactic (but no more distant than the elliptical), the largest of the others is distinctly blueish. They are classified as 'clumps' of molecular gas and each clump has its own identifier.

Delving deeper, it turns out that the clump at 10 o'clock is Minkowski's Object, nicely described in [1]. The origins of this object are still under debate (see [2] for a recent study). One suggestion is that is is a dwarf galaxy that is interacting with a radio jet from NGC 541 (and possibly from NGC 547 which is also a radio galaxy). The other is that it formed in situ from a gas cloud between NGC 547 and 541. In either case, the argument goes that it is being pushed to star-formation by a jet (possibly coming from a black hole in one of the two radio galaxies), hence its blueness.

NGC 457 is the lower of the two galaxies (the other is NGC 545) making up the obvious 'double galaxy', Arp 308 (aka VV 963).

 

As if that were not enough, the field is replete with spiral galaxies, mainly S0 types. Is it a coincidence that 5 of them have exactly 90 degree inclination (ie seen edge-on), or an artefact of some algorithmic processing? The galaxy with most visible structure is NGC 538 at the base of the shot. This is of type SBab(bar). 

This extended group is part of Abell 194, a close galaxy family centred on UGC 996 but so close as to be too large to fit in my FOV 😞

 

Martin

 

[1] https://sigmaorionis.wordpress.com/2011/07/19/minkowski’s-object-arp-133/

[2] https://arxiv.org/pdf/1703.03006.pdf

[Mike JW]

Hi Martin,

I have just had a very enjoyable read of the articles. I viewed these Arps a year ago but did not seek out any further information - glad you did. Minkowski Object  - how interesting and  re-looking at my original shot I should have pondered what was happening. Also I had not picked up that NGC 541 had at some point interacted with NGC 547 and hence the tidal stream between the two galaxies. Below is rather a messy shot (lots of dust bunnies had to be lost!) using the C11 from last year. If I get a chance I will point the 15 at it and see if I can get more of the tidal stream/cleaner view.

Mike

 

[Mike JW]

Arp 190 is an interesting object. Dr. Arp classified the pair as galaxies (not S or E) with filaments. However they both appear to be spirals. Arp thought the filament belonged to a third galaxy (the small white spot to the right of the lower galaxy) but this galaxy is likely to be a star in our own neighbourhood. Redshift puts the lower of the pair at about 475 million lyrs away but there is no info on the upper galaxy. The obvious elliptical below the pair has a similar redshift and might there just be a tidal stream between it and lower galaxy of the pair?

Colour images show the upper spiral as blue and the lower spiral as red.

 

Mike

[Martin Meredith]

Fascinating image. The upward-going tail is quite extensive compared to the size of the galaxy, similar to the Antennae at first glance. i see what you mean about the possible tidal stream. I look forward to observing this one.

Martin 

[roelb]

Tried to image Arp 190 and managed to see the tidal stream (going down and up to the right).

Indeed comparable to the "Antenna" Galaxies.

Celestron 6 SE

Bortle 7

ASI290MM

80/90 x 10 s

 

[Mike JW]

Always good to share each others observations.

Mike

[AKB]

Arp 113, small galaxy group in Andromeda.

C9.25 with Hyperstar and Ultrastar camera, giving f2.3 and a FOV in this view of 40' and 2.5" / pixel.

Taken on Nov 4, it's the group on the left hand side of the image.  But there's so much else to see here, including other galaxies, quasars, etc., all so much more understandable because of Jocular's plate solving and catalogues.  I've highlighted a few of the most, and least, visible.  Happy to see that PGC 3593057 is Mag 19.0

Tony

 

[Mike JW]

Hi Tony,

Good to see you are back in action. Excellent wide fov shot with so much on view.  Arp 113 was classified as Ellipticals and Elliptical like galaxies close to and perturbing  spirals. NGC 70 is the spiral and NGC 71 and  68 are presumably the E and E like galaxies but is there any perturbing on the go?

Mike

[AKB]

1 hour ago, Mike JW said:

Good to see you are back in action.

Thanks, Mike.  Nice to have the darkness back and the scope ready (but nothing going today!)

1 hour ago, Mike JW said:

NGC 70 is the spiral and NGC 71 and  68 are presumably the E and E like galaxies but is there any perturbing on the go?

Hard to say.  I've zoomed in a bit, but it's a bit noisy and you can see from the square stars that the Ultrastar's big pixels (6.45 microns) under-sample a bit (which I suppose means that my focus and collimation is actually not too bad.)

 

 

Edited November 5, 2021 by AKB

[Mike JW]

I looked at my shot from a year ago but it adds nothing to yours - no obvious interactions but as we know Arp got quite a lot incorrect. 

Mike

[Martin Meredith]

I love the field of view you're getting with the Hyperstar for the Arp 113 field! Just checked my Arp 113 -- doesn't add much.

[Mike JW]

Arp 216 (VV 329) lies in Pisces and the pair lie around the 215 Gyr away. Arp classified them as galaxies (not S or E) with adjacent loops - well, that is me confused. NGC 7882 on the left looks decidedly spiral to me - classified as SB(r)ab SY2. A very obvious bar and the bonus of being a ring galaxy. NGC 7679 on the right is given the SBO pec notation. Certainly it is peculiar (look at high resolution images and you will clearly see 'adjacent loops'. I picked up the one to the left and just a hint of the one that heads up. Some folk suggest these two are interacting but if that is the case then why does NGC 7882 appear intact? Maybe they are not interacting and NGC 7679 has merged with a dwarf galaxy causing the disruption?

The same shot below but with an interesting bit of fuzz labelled as 21.9 - no idea what it is. The two quasars are seriously distant. A 'z 'of 1.4 is around the 7.5 billion lyrs - remarkable.

Mike

[Martin Meredith]

Its a fascinating field. I note from a capture I made in 2019 that UGC 12628 (Sc, bar, diffuse) is just outside your shot to the lower left, and at 223 MLyrs it isn't so far away from the other two and might have had some role in the interaction.

There is a lot of 'fluff' in the environs of NGC 7679 potentially spread out in an arc between the two galaxies (there is a more diffuse patch in between NGC 7679 and the '21.9' object that is visible in my capture and in yours.

The 21.9 is from the quasar catalog (I only use the two orthogonal short lines for quasars) but lacks a redshift. I suspect that it just happens to line up with one of the fuzzy patches though I note that it has only a 77% chance of being an actual quasar so it might be some falsae detection which happens to involve whatever is going on in that patch!

I'm including my capture although it is (i) embarrasingly dusty and (ii) 28 mins exposure -- not sure why but perhaps I was trying to capture the mag 21.9 possible quasar

 

Martin

[AKB]

Arp 331, including NGC 380 and friends – too many to count, really.

Also in there, I've labelled PGC1999169 and PGC2001155 about 1,600 Mly away and Mag 18.

Also, a quasar there too.

Tony

Edited December 2, 2021 by AKB

[Mike JW]

Hi Tony, wonderful wide field shot.

I always enjoy a visit this Arp - classified by Arp as a chain of galaxies but how many in the chain? He listed 8 in the chain from NGC 384 to NGC 379 but some folk think he also included 373, 375 and 388. Below is my shot of the main chain of 8 - rather much drift as evidenced by the black around the main view. This chain is also special because it is a chain of elliptical galaxies.

Mike

[AKB]

Thanks for that, Mike.  Really informative.  

I must try harder… but that presupposes a certain level of knowledge which I don’t possess!

Tony

[Martin Meredith]

Just compared this to a 7m (21 x 20s) capture I made a year ago. Yours (and Mike's) is just so much deeper! I see that I noted some high cloud so maybe that accounts for a small part of it. You're getting about 80% more FOV than me too which makes a big difference. Great to have these comparison shots.

 

 

[roelb]

Arp 331

6 SE @ F/5

ASI290MM

Bortle 7

28 x 10 s

[Martin Meredith]

Here's Arp 200 from last night. I was mainly testing out the new cam and also interested to see how much effect the moon would have. I don't normally observe galaxies with a bright moon in the same quadrant but clear nights have been few and far between recently.

This comes under the 'material ejected from nuclei' category in Arp's catalogue. I can't quite see what material is being referred to myself. I see a couple of bright spiral arms, with knots, plus a faint halo. I assume the other arms are out of view as the galaxy has an estimated inclination of 77 degrees.

Out of interest, the PGC galaxy next to the close pair is mag 16.2 and the annotated m19.2 quasar is borderline detectable, so certainly not a washout for galaxy observing, though some way from optimal.

Martin

 

[Mike JW]

Observing in strong moonlight is often a sign that we have had a run of poor weather - certainly true in this case. You did well to get the detail. (I was lunar sketching).

I looked up my visit to this one - also a 'desperation' to do something - it was windy so I had to do 3 sec subs and delete about half of them.

Similar detail to yours but slightly better resolution. The quasar is better defined.

Mike