This is a reshoot with twice the exposure time under a bit better seeing. Original post: http://cosmoquest.org/forum/showthre...115281-Arp-178
It didn't pick up much more of the plumes than the first but detail in the galaxy is far better. Some of the text below is from the initial post but there is something new in this image so keep reading as it is near the end. It is not in the original nor is it an asteroid or other solar system object.
Arp 178 consists of three galaxies NGC 5613 (upper), NGC 5614 (lower) and NGC 5615 (inside NW halo of NGC 5614). These are located in the constellation of Bootes. NGC 5613 is nearly 400 million light-years distant while the other two are a bit less than 190 million light-years away. Arp put these in his category of galaxies with narrow counter tails. His comment reads: "Ring off center, broad ejected plume from condensation in ring."
Most papers of the era of Arp's Atlas and prior consider NGC 5614 as interacting with the northern galaxy (5613). We now know that with 5613 having over twice the redshift this isn't the case. It is unrelated but worthy of its own entry in the atlas. It is classed as (R)SAB(r)0+ by NED and the NGC project agrees but leaves off the + sign. At first glance it appears to have a faint outer ring. But look closely and you see it is really two very extended spiral arms that nearly overlap. One starts at the 11 o'clock position and goes around to the 4 o'clock position. The other starts at 5 o'clock and goes around to the 10 o'clock position. In both cases the ends are further from the core than the other arm inside it. This may be easier to see in the Sloan image stretched a bit differently than my image. What caused this? There seems no likely source. Prior to its redshift being determined it is easy to conclude that NGC 5614 caused it. Now it is a puzzle.
The main feature here is NGC 5614 a very large tightly wound spiral with an off center core and huge plume. NED and the NGC Project classes it as SA(r)ab pec. The plume seems possibly related to NGC 5615. It certainly is due to a gravitational interaction in the recent past. The off center core causes Arp's "ring off center" comment. At first I thought it might be that this was a case of a merger with inner arms rotating counter clockwise and outer ones turning clockwise but I found a rotation curve that says all are rotating the same way. It is just the core being off center from the first ring that create this illusion. I am having a hard time seeing it. Still I believe it a merger in progress with NGC 5615.
The condensation Arp refers to is NGC 5615 and has a redshift that puts it about 3 million light years more distant than NGC 5614. NGC 5615 is not classified at NED, NGC project says S? I can't see enough to try classifying it so have to agree with NED. Is NGC 5614 in the process of digesting NGC 5615. I saw suggestions of this in early papers but nothing conclusive. One paper suggests that the tightly wound arms of NGC 5614 might be due to an unusually massive black hole at its core. No reason given other than it appears such galaxies tend to have larger than expected black holes when this has been measured. Pretty speculative to me. In any case it is an interesting galaxy as is NGC 5613.
After I wrote this Adam Block posted an image of this galaxy taken by the 32" scope at the Mt. Lemmon Sky Center observatories. It clearly shows NGC 5615 is broken into several bright cores. It also shows the bright blue arcs in NGC 5614 far more clearly. I now think 5614 is quite likely the remains of a galaxy torn asunder by 5615, even the core of it is being ripped apart by tidal forces. I wrote Adam with this suggestion and he agreed it is likely the case. The three million light-year difference in redshift is likely due to relative motion and difficulty of assigning a redshift based distance to a mess like this.
Another galaxy at about the same distance of NGC 5514-5 is to their NE. Several galaxies of the same distance as NGC 5513 are in the frame. It appears they are two different groups. Several galaxies at 1 billion light-years are also found around the image. While several more are at 2.1 to 2.2 million light years and may make a third group.
Normally I think of NGC galaxies as being closer than say a half billion light-years, far closer in many cases. But NGC 5609 at 1.31 billion light-years is an exception. NED lists its green magnitude as 16.3 while the NGC Project puts its visual magnitude at 15.7. Since green is usually used for this I can't explain the difference. Still this one should be visible in larger amateur telescopes from a dark site, say a 16" or larger. Young eyes may glimpse it with less aperture if the brighter magnitude is correct.
The smudge of a galaxy north northeast of Arp 178 is SDSS J142418.67+245549.8. NED says it is only about 6" of arc across though it is about 24" across in my image. NED also gives it a far too faint magnitude. It has no redshift data. Except that its position exactly matches that of NED I'd think they were talking about a different galaxy.
Southeast of Arp 178, below a galaxy at 2.2 billion light-years is an object marked by a question mark. NED lists it at 22nd magnitude. Indeed it is 22nd magnitude (barely visible) on my first image of this field but it is 19.5 magnitude on this image or 10 times brighter than that in my first image. There is a galaxy at that position. That got me wondering if a supernova had been seen at that position. Yep, it is PTF11dwn. PTF stands for Palomar Transient Factory. 11 is the year (apparently they don't worry about 2100 and beyond). The letters dwn denote its position in objects the PTF turns up. First is a, additional letters are used as needed. Since it turns up a lot of other things than supernova the next one it found was PTF11egs rather than PTF11dwo. I didn't look up what that would be. The supernova is a type 1A at magnitude 19.5. It is in SDSS J142422.29+344833.8. It was discovered on May 23rd. My independent discovery image was taken on June 5th, 13 days later. I wonder how many others like this are lurking on my images I'll never know about since I have no comparison image. Even if I did finding, it is highly unlikely. Only because it was near a galaxy I was annotating did I notice it. When comparing the NED image of the field that extra star in my image confused me for a bit. Otherwise I'd never have noticed it.
Adam Block's image with the 32" telescope at the Mt. Lemmon Sky Center
14" LX200R @ f/10, L=4x10' RGB=2x10'x3, STL-11000XM, Paramount ME