Merger Feedback. Post your comments here.

[aholinch]

hi
the latest one : SDSS 587739721376202860 looks very easy, but actually it's one of the most difficult mergers to simulate.
The fact that the black and white pictures have almost no features don't make this any easier.
Almost 50 % (or more) of the sims looks like this merger and there is no way with this level of (non existing) details to make it any better
Sorry
E.

You're right about how the ones without tails are difficult to match.  For me, the most noticeable feature is how the the core of the bottom galaxy is off-center from the rest of the disk.  Trying to match that bit of stretching is tough.  I've had a little bit of luck increasing the number of particles to see some more detail in the simulation.  But doing that causes things to run a little slower.  We're trying to see what types of merger features we can capture with the current setup.  So, even if we don't get the best matches on some of these disk-only distortions, at least we'll have any idea of which orbits in general can cause that type of distortion.

Thanks for giving it a go even on the tough ones.

[echo-lily-mai]

Oh that’s a tough one !    
http://cas.sdss.org/dr7/en/tools/quicklook/quickobj.asp?id=587724234257137777

[ElisabethB]

Oh that’s a tough one !    
http://cas.sdss.org/dr7/en/tools/quicklook/quickobj.asp?id=587724234257137777

Yup 
I've been trying for a while but it doesn't look good ! 

edit : better keep this one up for a couple of days ! It's really difficult
Okay Echo ! 

[echo-lily-mai]

Oh that’s a tough one !    
http://cas.sdss.org/dr7/en/tools/quicklook/quickobj.asp?id=587724234257137777

Yup 
I've been trying for a while but it doesn't look good ! 

edit : better keep this one up for a couple of days ! It's really difficult
Okay Echo ! 

Hi Els good to see you,    yes I thought I would just quickly do one and have a cup of tea, but I think it wanted a little more concentration! I'll give it another go later.

It’s hard to ignore the bridge, is it a broken 3rd arm or disturbed 2nd arm, i don’t know? if you can match it it throws everything else out, but i was only on it for a short time maybe a couple of days are needed! 

[graham d]

Definately difficult. Thanks Echo and Elizabeth. Your posts prompted me to have another and more productive attempt

[echo-lily-mai]

Definately difficult. Thanks Echo and Elizabeth. Your posts prompted me to have another and more productive attempt

Oh that’s great Graham you must let us know if you manage to crack it. 

[thaumielx72]

Hello fellow merger fans.

I have been trying to set aside time each day to help with the 'science of Mapping the galaxy' and mergers seems to be a really dynamic thing to study.

I can not help tendering to you one thing that would make Merger Science more dynamic and would perhaps not swallow up too much programmer time.

Colors!







(And now an explanation of what makes me such an idiot...)

[rant begins]

I started in mainstream, business oriented IT back in 1979.  A few years later IBM released the "stupidest toy" a serious business company ever considered - the IBM Personal Computer.

Starting in 1983 it became my "job" (more like a hobby I got paid for) to take these silly machines and put them on desktops all over the building.  The usual response was like I had placed a live cobra on their workspace between the pictures of their kids and where they do actual work.  They were used to getting serious looking print-outs from us and only the section chief ever worked with what they called 'a computer,' meaning the dumb terminal connecting their office with our Data Processing Center.

Once they realised it wasn't likely to blow up and kill them they started getting actual work out of their PC's.  Some even became quite adept and became even more efficient workers than they had been before the PC came along.  The Personal Computer revolution had come to our school district.

What was the one overwhelming thing that sold these serious business types and their secretaries on this travesty of turning their jobs over to these heretical gadgets? 

Colors.

Not only were their jobs more fun now (and 'MY Computer' a serious office toy, I mean tool) but they realised they could process what they were seeing on screen quicker.  They could even show others who had no legitimate interest in someone else's work what they were talking about as different colors made the different data quicker to understand.

But mostly, it was the students who now became interested in their lessons faster.  Because colors made the whole boring idea of learning more fun and easier to grasp quicker.

[/end of rant]

[aholinch]

I can not help tendering to you one thing that would make Merger Science more dynamic and would perhaps not swallow up too much programmer time.

Colors!

Yes, I totally agree, colors can help make the simulations much more interesting.

To add colors to the simulations to represent the observed colors would require much more involved calculations including gas and stellar evolution.  However, there are several other ways to incorporate colors.  One is to assign an arbitrary color to the particles belonging to each galaxy.  That allows you to observe interesting effects, such as mass from one galaxy being captured by another.  This can sometimes be confusing for people observing the simulation.

There are two ways that we do use color in the current merger applet.  Both are accessible from the enhance tab.  To activate them, right-click (or shift-click) on the big simulation panel.  You will have options to blur the image, color by z-velocity, and one other.  The color by z-velocity option will show the particles moving towards you as blue, the ones away as red, and the ones in the middle as purple.  There is another color option, but you need a certain type of eye wear to take advantage of it. 

HTH,
Anthony

[Quialiss]

I've gotta say, the current merger target(587724234257137777) really challenged me, and I see I'm not the only one..  This is my best match, what do you guys think?  The whole angle of the main galaxy is off, I tried to fix it but the difference between the correct angle and something wildly not is minuscule, and my hand isn't quite steady enough to find something closer.
Crazily enough, in my sim, the arm at the bottom and the detached one up top, the two features I told myself I -had- to match, don't actually 'exist', they just happen to be areas where the warped disk overlaps itself and looks more solid.   

[graham d]

That's a nice match Thialiss . Anthony's colour scheme prompted me to have another( 3rd) attempt, Lily. I got another close match, the z colour value certainly helps you to acquire the 3D perpective of the merger. I didn't get to level 3 this time-drat! Why? I just had to manipulate the Depth function

Anyway, I was thoroughly impressed with the colour function and will use it again. The blur function made the image intensity much lower when used in conjunction with colour.

[echo-lily-mai]

I've gotta say, the current merger target(587724234257137777) really challenged me, and I see I'm not the only one..  This is my best match, what do you guys think?  The whole angle of the main galaxy is off, I tried to fix it but the difference between the correct angle and something wildly not is minuscule, and my hand isn't quite steady enough to find something closer.
Crazily enough, in my sim, the arm at the bottom and the detached one up top, the two features I told myself I -had- to match, don't actually 'exist', they just happen to be areas where the warped disk overlaps itself and looks more solid.   

Quialiss that’s interesting, my ones seemed to end up with three arms even if you could only see two? Different mergers I have worked on have had a similar effect to what you have explained here. So I know what you mean.
Nice match, I love seeing the sims that have been worked on.   

[graham d]

Diabolically curved rings today. I was disatisfied by my attempts to get a decent simulation. Any hints? We see rare-common ringed galaxies alone. The chance of a merger of two ringed galaxies is rare but in these simulations we do see that rings may be generated during the merger process.

[lpspieler]

Hello all,

I just did a few simulations on the new double ring target. There were quite a few simulations that looked pretty similar to the target (Nothing came, of course, even close to the solution ElisabethB posted in the corresponding OOTD thread  ).

But when I looked at them in the enhance tab and turned them around in 3d, they all turned out to be overlaps of distant galaxies. I didn't even manage yet to get the galaxies to come closer together, no matter how I tweaked the parameters.

Now my question: Has anyone considered the possibility that the two galaxies in the target could in fact be overlapping? I mean, we don't have a spectrum for one of them (not even in NED), and the two rings look suspiciously undisturbed...

cheers

[graham d]

That's what I thought too lp, that no matter how improbable they were overlaps, undisturbed. I was part convinced that you could generate the two ringed forms upon merger with my own average attempt, which almost convinced me that they were infact mergers. What clinched it, as I mentioned in today's OOTD, was Elizabeth's incredible mind blowing image. I hope that she can give us some procedural hints, she has Paganini's touch. I still thought these computer simulations had a good measure of some black art until Elizabeth's touch came along. If you are listening Elizabeth you have to redo it and post another image as a self consistent proof. I'll have another go.

[ElisabethB]

Now there is a challenge ! 
I'll give it another try, but it really was a combination of looking at a lot of sims and then fiddling a bit with this one. I came as a surprise to me too ! 
But I'm going to try for another one and I'll blame you guys for my lack of sleep