ARP GALAXIES

[Mike JW]

A satisfying result Bill. Well done. I like the idea of nipping into the kitchen. I do the same. A pity we cannot now re-organise the thread and put all the Arp 104 shots together.

Mike

[Mike JW]

5/09/20 - after a long run of cloudy nights I managed to grab an hour as the bright moon began to wreck the sky. I call this desperation astronomy. I know there will be poor images due to the moonlight and humidity........but in GB if you don't grab these chances then weeks of no observing become months.......

ARP 46 in Pegasus.

At first glance, I thought "this Arp is the galaxy pair" - wrong and right at the same time. The right hand spiral (actually a barred spiral - just got the bar and also a hint of a dark lane) is UGC 12667 and lies about 200 million lyrs away. Arp 46 is the left hand spiral - UGC 12265,  (mag 15.1) and is classed by Arp as 'spiral with a high surface brightness galaxy on its arm'. High resolution images clearly indicate interaction between this galaxy pair. They are about 230 million lyrs away. UGC 12265 is classed as SB (rs)d pec,-loosely translated it is "all messed up" and to be more precise - barred spiral, with loosely wound arms, making a transition to being a ring galaxy and peculiar (messed up structure).

Mike

[Martin Meredith]

Interesting pairing as you say. Cases like this where one is somewhat further way than the other give a real feeling of depth, especially as they appear to have a similar actual size. Thanks for the detailed description.

When I saw the Arp number (46) at first I thought we were in true ring galaxy territory but I am out by 100... 

Martin

[Mike JW]

06/09/20 - Here I am, one night later and this was serious desperation astronomy. I had time for just one target before it clouded up but well worth it.

ARP 86 in Pegasus. Like Arp 46 this was classed by Dr Arp as " spiral with high surface brightness companion on arm". It is NGC 7753 the big spiral and 7752.

This pair are about 272 million lyrs away and are gently interacting. Most likely 7752 has done a flyby and presumably will get pulled back towards 7753. This pairing are of the M51 type = grand design spiral with a small compact high surface brightness companion on an arm. These guys belong to the sub-class ; "close but still not perturbed". (The other sub class is where the pair have been seriously perturbed.) High resolution images show that the bridge to the companion has definite blue patches, implying star formation due to the companion stirring up and compressing the inter stella gas/dust. I picked up some of the star forming regions in 7753 and I was pleased to get the bridge across to 7752.

7753 is SAB(rs)bc. 7752 is IC (irregular compact and low mass). 7752 is very bright for its size . Studies suggest this is due to material being dragged from 7753 as it passed by. The main perturbation occurred about 600 million yrs ago as 7752 swung by and crossed the galactic plane of 7753 in a low eccentricity path .  50 million yrs ago it crossed back through the galactic plane.

http://www.spitzer.caltech.edu/images/6566-ssc2019-03a-Galaxy-Merger-Arp86 - is well worth a look where we can see much star formation (blue). Also, take a look at the bridge - it has two distinct trails of stars. Also note just how bright and lumpy 7752 is - not a quiet place to live. (Also the details below the image labels 7753 as 7752.......)

Despite the short session, it was well worth it to get the interesting shot and then to read up about it. That summarises why I enjoy the EEVA approach - use the camera to observe a target, then find out something about it, rather than spend the time and effort to get an image to then move onto the next image...............

Mike

 

 

Edited September 7, 2020 by Mike JW

[Martin Meredith]

Beautiful image and description. Having checked out the amazing JPL image I can make out the start of the twin tails in your shot. There's a nice challenge to see how much of those tails one can pull out. I'd like to visit this one in colour. The Lodestar has quite good near-IR sensitivity apparently.

I do have a shot of this from a few years ago -- quite poor in comparison with yours (also taken in September I see). It is much smaller than it appears in your zoomed image. You're getting some remarkable detail in 7s subs.

cheers

Martin

[Mike JW]

Thanks Martin, As you know when I use the 15", I am limited to about 7 seconds because it drifts too much. However I do like using the 15 because of its large light gathering capacity. Your shot of Arp 86 complements mine as it gives the wider fov and hence the context of the galaxy pair hanging in space. Strip down of the 15" Dob today and mirror clean up time - hate cleaning the mirrors but it has to be done.

Mike

[Mike JW]

I was out there again last night and amongst other targets I re-visited Arp 86 and this time I used 11s subs and let it run whilst I was busy looking at info on other targets.

A smoother shot maybe, but not significantly better.

[Martin Meredith]

More or less simultaneously (we are one hour ahead, at 23.30) I was also looking at Arp 86, initially in mono, then with some colour added in. The left pair of shots are 3 minutes total in 15s subs. Top right is 11 minutes (2 mins in each of RGB and 5 in L), but viewed in mono. Bottom right is 8m 15s shown in colour. There is a little more coming out in the longer inverted exposure -- the background is smoother so a few more details of the fainter parts are visible. The colour version doesn't add very much but more detail of the companion galaxy is visible in the colour shot, presumably due to the reduced transmissibility (the companion is pretty bright in luminosity). Like yours, these are also using hyper stretch.My stars are noticeably squarer close up! 

[Mike JW]

Great to have your input as well. Agree colour adds very little - to be honest I prefer the mono shots. Although the colour version picks up some of the companion detail in my second attempt.

Mike

[Mike JW]

ARP 212. (8/09/20)

Arp 212 ( NGC 7625) is a great  contrast to Arp 86. There are a variety of classifications - Ep, SApec, SO. Essentially it is 'a turbulent elliptical with dust'. There has been various studies of the dust content of this galaxy, which on reading I failed to understand. However these studies have led researchers to conclude that 7625 is the result of a merger, possibly of a similar sized companion. (There is no obvious nearby galaxy candidate for a fly by, thus the merger theory is favoured.) The companion would appear to have been well and truly 'eaten', such that little obvious remnants remain. The high level of dust could be obscuring the remains of the companion. However there is much 'indigestion' - dust appears to radiate out from the bright centre, with centres of star formation. There has been much starburst activity in the past but it has now passed its peak. However there are massive stars being formed within the dusty regions. There are more H alpha emissions to the north of the nucleus (up in my shots) - suggesting star forming activity? There is also a ring but it has a high dust content and low star density thus it is faint (not visible) in visible light.

Below are two shots. The left hand wins the 'pretty view' award (I do love diffraction spikes) and the close up shows more detail.

Mike

PS cleaned the mirror yesterday - so no dust bunnies.

[Mike JW]

Here is my second Arp from last night.

Arp 182 is the pair of galaxies NGC 7674 and its companion 7674A. You get a lot for your money with this Arp because it is also part of the compact group – Hickson 96. NGC 7674 is SA(r)bc pec and its companion is a tight spiral Sa. 7674 is also Sy2 (seyfert 2) – meaning it has very active nucleus (very bright nucleus and a bright source of electromagnetic radiation). Sy 2 galaxies have the nucleus obscured by dust. Amazingly so 7674 has two gigantic black holes about 1 lyr apart suggesting a merger of two galaxies in the past. I was hoping I might pick up the two beautiful plumes that curve away either side of the companion.

HCG 96 includes the Arp pair, the little galaxy below and to the left and further to the left NGC 7675 (elliptical).

My shot also includes LEDA (PGC) 21460, another Sy2 galaxy. – mag 17?.

By the way Arp 182 is also VV 343.

Some of the other fuzzy spots are probably galaxies.

Mike

[Martin Meredith]

Fascinating to hear about these plumes in NGC 7674. They sound like a real challenge. I'm trying to ID the PGC galaxy but I have it down as PGC 214960 (mag 17.4). Here's a shot of mine from long ago when I was still using my colour Lodestar. Some dust bunnies here, and colourful hot pixels. Also, a rather sleek flat galaxy in the upper right (must be PGC 71461).

[Bill S]

Martin,

Here's a plate solved and annotated version of your shot. PGC 214960  is marked.

 

Hope this helps.

No observing last night but the previous night one of the objects I was looking at was Arp 86 and at about the same time as you and MikeJW.

 

There's a lot to see in Pegasus.

 

Best regards

Bill

 

[Mike JW]

How strange that we should be targeting Arp 86.  Mike

[Mike JW]

Arp 284.

Not for the first time I visited Arp 284 last night (13/09/20). However first time with the Dob and those diffraction spikes of 16 Psc do it for me. Personally the view as captured below gives me an aesthetic buzz - so much to enjoy.

16 Psc - is a spectroscopic binary, mag 6, a yellow-white dwarf star on the main sequence.

Follow the diffraction spike that goes up and to the left. It leads you to a bright star, now go straight down and you see a grey fuzz, about half way to another less bright star. This is Q 2333+019 10.17, z=1.871 (light travel time = 10.185 billion lyrs!!!) - images show it as blue (not surprising as it must be bright). 

Finally to Arp 284, classed by Arp as having infall and attraction (still do not understand what is meant by this)

NGC 7741 = SB(s)b pec (on the right) and 7715 = Im pec sp. The pair are about 100 million lyrs away.

 7714 is a starburst galaxy and hence strong H alpha (red colouration). It has an active black hole at the centre. Astronomers characterise NGC 7714 as a typical starburst galaxy  composed of Wolf-Rayet stars — extremely hot and bright stars that begin their lives with dozens of times the mass of the Sun, but lose most of it very quickly via powerful winds.

The two galaxies drifted too close together between 150 million years ago, and began to drag at and disrupt one another’s structure and shape. Apparently 7715 charged right through 7714

As a result, a ring (older sun like stars - picked up in my shot) and two long tails of stars have emerged from NGC 7714, creating a bridge between the two galaxies. This bridge acts as a pipeline, funnelling material from NGC 7715 towards its larger companion and feeding bursts of star formation. Most of the star-forming activity is concentrated at the bright galactic centre.

Mike

[Martin Meredith]

Beautiful composition, Mike. I also love diffraction spikes (although mine display evidence of a twist which I really must sort out). 

There's so much going on here. I can see the tails and counter tails, more so after consulting Kanipe and Webb's Arp Atlas. There is a double tail (presumably one tail from each galaxy?) joining the two. I had a quick skim to see if 'infall and attraction' is defined but didn't spot anything. I did see a note that 'characterisation of peculiarities is sometimes descriptive rather than literal' but that still does help. Perhaps the term is defined in the original Arp atlas.

A little mystery about that quasar: I've consulted my charts and I see two quasars hereabouts. PB 5468 is further in with mag 18.3 and the redshift of 1.87, which is the value you cite. I have Q 2334+019 as further out with mag 18.6 and a redshift of 2.19, making it still more distant. It is entirely possible that the data has been changed since I created the charts though. I have noticed that quasars (mainly their distances) are updated somewhat more frequently than other objects.

Martin

[Mike JW]

Here is Aladin with NED overlay. The cross matches the grey fuzz on my shot and has the data as Q 2333+019 - redshift 1.871.

I have inputted PB 5468 - it seems to put the cross at the same place as the quasar? see second screen shot.

Mike

 

 

Edited September 15, 2020 by Mike JW
new data

[Mike JW]

In the early hours of 24/09/20 I took advantage of the transparent (but unsteady) sky as the cloud and rain left the area.

Spoilt for choice of targets so decided to concentrate on Arps - nine in total. Each one has a different character which is why I enjoy the Arp journey. My favourite from the night is Arp 331 - a galaxy chain. Arp 228 is showing a ring structure. Arp 290 shows the 'wind blown' effect. Arp 333 - just like it but Arp thought it had thin arms. Arp 229 is a superb SA galaxy (and a radio source) with its small EO companion. Arp 219 - what a great tidal arch due to its interaction with its tiny neighbour. Arp 186 is a recent merger with the tails very much in evidence. Gradually they will disappear. Arp 126 is a pair of messed up spirals. Arp 70 is a pair of interacting galaxies - note the small galaxy at the end of the tidal tail.

Mike

 

 

 

 

 

 

 

 

 

 

 

 

 

[Martin Meredith]

I prepared a list of Arps for last night and working my way through them had to discard the first 4 or 5 as they were actually also Hicksons that I'd already observed... I managed a few before getting clouded out, and Arp 113 is the most appealing and perhaps the most interesting too. It is also known as VV 166 and I suppose this name should take precedence, although the NGC 70 group, as it is also called, has been known since at least the 1930s.

This group belongs to the "Elliptical galaxies close to and perturbing spirals" section. In the labelled plot (N up) the numbers are NGC designations. NGC 68 and NGC 71 are type E-S0 (elliptical/impossible to tell if there is a bar), while NGC 70 and 72 are clearly spirals, types Sbc and Sab respectively. I have NGC 70 and 71 as having active galactic nuclei -- both are Seyfert type 2 (I'm not sure what the type 2 means).

The distance estimate for this group is intriguing. Most of the members (including the outlier NGC 74) have distances in the range 325-345 MLyrs. This is also the case for the mag 15.7 galaxy on the extreme left hiding in the shdow of the bright star, so it is a group with a very dense core cohort and some further flung members.

However, NGC 68 -- one of the main players, visually -- is estimated to be at 278 MLyrs. Looking around for any information about this group, I came across an article entitled Galaxy collisions in dense groups with Hickson as lead author which mentions that one galaxy in NGC 70 has a discrepant redshift. [1] There is an older paper that discusses the discrepancy in more detail [2], concluding that it is most likely not a member. Thus it appears we are left with a very pleasing chance lineup.

cheers

Martin

 

[1] http://articles.adsabs.harvard.edu/pdf/1977ApJ...213..323H

[2] http://articles.adsabs.harvard.edu/pdf/1974ApJ...193...19K

Edited October 6, 2020 by Martin Meredith

[Mike JW]

Hi Martin, I love this group and a pity I lost my original image of this Arp. Also well remember squinting in the 20 to see these galaxies and great to see your shot and as you indicate there is much to absorb in this group.

Mike

[Mike JW]

Last night I wandered through the Arps in Aquarius. I finished on Arp 295. I knew they had a long connecting filament but also knew I would have to go beyond my customary 5 minute total time. I decided to let it run whilst I began clearing away the chaos of an observing session and walked around to warm up my shivering body.

Arp 295 is a Zwicky Pair. Both are spirals and are about 285 million lyrs away. The lower one looks like it has small dwarf galaxies at each end - it doesn't. To the right of this galaxy are three dwarf galaxies in a line at a similar distance. I picked up the obvious first galaxy, hint of the second. Other galaxies in the shot are also around the 280 million lyrs away.

To my delight and amazement I actually picked up a hint of the filament linking the two and the brighter filament heading down (south) from the lower galaxy.

Looks like the corrector plate needs a dust off/clean. Hard to find the best settings because this crowd are low down in the murk here in GB.

Mike

 

[Martin Meredith]

Good catch! Arp 295 is a fascinating pairing with the bridge and counter-tail. It is definitely worth 11m 40s of anyone's time!

I observed this some years ago when I appear to have been already experimenting with a circular orifice (this predates Jocular so would have been processed in GIMP to do the inversion). I will definitely we revisiting this soon if it clears up before Aquarius is lost for the year. You're getting better resolution of the lower galaxy than I can manage.

Here's a short article from 1974 by Alan Stockton discussing the tidal origin of the bridge.

1974ApJ___190L__47S.pdf

cheers

Martin

[Mike JW]

Thanks Martin, it would be good to point the 15 at it but it is too low for the Dob. Interesting article - much to learn as always.

Cheers,

Mike

PS. Below is a screen shot from an article  https://core.ac.uk/download/pdf/33108853.pdf 

Shows the anatomy of the pairing - a tail, a bridge and a clumpy plume. The stars in the bridge are thought to be new stars formed by the tidal interaction as the northern galaxy passed by. It appears that there are not any stars in the bridge that have been pulled out of the galaxies.

Edited October 10, 2020 by Mike JW
added more info

[Martin Meredith]

Here is the NGC 80 group which contains Arp 65, as indicated (I have it as NGC 90 but I read that it is actually NGC 91). There are no fewer than 9 NGC galaxies in this shot, which incidentally lies just to the south of Shakhbazian 364 (the weird IC 1542 lies just at the middle-left edge in this shot). This is 16 x 20s = 5m 20s total exposure. 

Arp 65 is classified as 'spiral with small high surface brightness companion on arm'.  Kanipe & Webb's The Arp Atlas of Peculiar Galaxies identifies 3 possible companions, all of which are some way from the galaxy core, and are identified on this close-up (North up):

 

Companion 1 is magnitude 18.0 but the other two are quite a bit fainter (no data found so far).

Article [1] goes into Arp 65 in some detail, and looks at the evidence for an interaction between NGC 90 and the type Sab NGC 93 seen at the top left. Their figure 1 gives a good detailed view of this system, and shows a clear tail reaching all the way to comp 3 (not seen in my image). A higher-resolution attempt at this might show up more features, including a better look at the fork in the southern tail. There is certainly a lot more going on here than in my image.

Martin

[1] https://arxiv.org/pdf/1509.02614.pdf

 

 

[Mike JW]

Recently I too took a look at Arp 65 with the C11 - the fov being much smaller than Martin's set up. However the increased aperture enabled some of the tidal tail that goes to companion 1 to be picked up. I think also I have a hint of companion 3 and a definite for companion 2

Mike