Author Topic: Thursday 19th February 2009: Barred Spirals and Bar Evolution  (Read 4093 times)

Alice

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Thursday 19th February 2009: Barred Spirals and Bar Evolution
« on: February 19, 2009, 12:33:23 am »
Thought I'd use today's Object of the Day to introduce our many new Zooites to some of the things we get up to here. Galaxy Zoo Get-Togethers have been a tradition for a little over a year; our most recent was to Astrofest, where some of us attended some excellent lectures. One, by Johan Knapen, was about barred spirals, one of the questions we get asked in Galaxy Zoo 2:



Bars are present in more than half of all spiral galaxies. It is not clear why they form. While it seems logical that a star should travel around in a circular orbit, the stars in bars travel round more in a boxy or sausage-shaped orbit - which is perfectly stable. In fact, stars can orbit in all kinds of crazy patterns, and once they're there, they'll keep doing it. What makes them leave the circular or oval path and head into a more rectangular one in the first place is less obvious. It seems to be some instability in the galaxy itself.

According to the lecture, a timeline of the evolution of the bar in a spiral galaxy would go something like this:

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The galaxy starts of as a smooth disk-like spiral; then gradually the bar grows and grows, the arms emerging from its ends. But, of course, we don't know this for certain - because a bar would take several million years to form. This is one of the ways in which Galaxy Zoo comes in handy. We can't watch evolution taking place, but we can map the fossil record; and, similarly, we can use the massive amounts of data and our eyes to look at many, many galaxies and one day see if we can place them on such a sequence. Maybe the above is right, and maybe it's wrong.

If you found this interesting, you can see a more detailed write-up of my lecture notes here. I personally think we can get several very informative Objects of the Day out of that talk; anyone like to find some examples (or indeed counterexamples) and write more?

You can check out lots more beautiful barred spirals here.

P.S. For an authentic look at my lecture notes, here some of them are along with my devoted assistant Cassie. Note messy piles of astronomy related stuff all over the table.
« Last Edit: March 08, 2009, 12:43:18 am by Alice »

Lovethetropics

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #1 on: February 19, 2009, 01:43:15 am »
Thank you Alice for taking notes on that lecture and sharing them with us.  It's wonderful to see the evolution of barred spirals.  Really important OOTD.  It shows new and old zooites how we are contributing to science and what those scientists are doing with our contributions.  :D

 *and find lots of asteroids  ;D

Caro

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #2 on: February 19, 2009, 07:28:56 am »
This is wonderful Alice.  ;D
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Geoff

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #3 on: February 19, 2009, 08:25:23 am »
Interesting OOTD, more work needs to be done on bars (and in bars probably  ;D ) to find out how they form and what they add to galaxy morphology.
  Sometimes I think we're alone. Sometimes I think we're not. In either case, the prospect is staggering!- Arthur C. Clarke

Pat

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #4 on: February 19, 2009, 08:44:32 am »
Well done Alice. :) Another great OOTD. :D

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hgp88

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #5 on: February 19, 2009, 09:10:14 am »
I think that the images shown by Alice are very interesting and show galaxies with bars of different sizes - it seems that we are taking a leap to say that they represent a time evolution.  Is it not possible to simulate bar formation in a galaxy?  I have certainly seen a simulation showing colliding galaxies (I think it was by a group in Durham, UK) and a mechanism for ring formation etc.  I appreciate that there are issues with producing a simulation that contains billions of interacting points, but if it is possible it seems worth doing (if it hasnt been done already).  Maybe then we will see why bars form in some galaxies and not others and probably more importantly what evolution takes place after bar formation.

weezerd

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #6 on: February 19, 2009, 09:33:33 am »
Love it!   ...and thank you Alice for taking all those lecture notes, you give those who didn't attend a chance to taste the flavour of the Fest! (Not to mention enjoying the fruits of your follow-up research!  Go girl, go!!
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Alice

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #7 on: February 19, 2009, 11:07:44 am »
Interesting OOTD, more work needs to be done on bars (and in bars probably  ;D ) to find out how they form and what they add to galaxy morphology.

;D ;D ;D ;D ;D

I think that the images shown by Alice are very interesting and show galaxies with bars of different sizes - it seems that we are taking a leap to say that they represent a time evolution.  Is it not possible to simulate bar formation in a galaxy?  I have certainly seen a simulation showing colliding galaxies (I think it was by a group in Durham, UK) and a mechanism for ring formation etc.  I appreciate that there are issues with producing a simulation that contains billions of interacting points, but if it is possible it seems worth doing (if it hasnt been done already).  Maybe then we will see why bars form in some galaxies and not others and probably more importantly what evolution takes place after bar formation.

Johan Knapen showed us a brilliant video with just such a simulation. Unfortunately he doesn't seem to have a webpage and I didn't get the reference for the video, so I can't reproduce it. I've tried to reproduce it in SDSS galaxies. It intrigued me that the arms first evolve into 2 very distinct arms, and then into that steering wheel.

But I don't know if the video or indeed my  representation are correct. This is guessing, not gospel! I think we can help with just such research if we carry on being the success that we are . . .

stellar190

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #8 on: February 19, 2009, 11:59:26 am »
fantastic ootd ;D ;D ;D ;D

adamprimus

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #9 on: February 19, 2009, 06:29:26 pm »
Thanks Alice. I have noticed while classifying in GZ2 that there appear to be more barred galaxies than were apparent in GZ1.
I wondered whether this is actually the case or whether I am now simply more conscious of these features than I was in my salad days of GZ1... :-\


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Half65

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #10 on: February 19, 2009, 06:33:31 pm »
Great OOTD Alice.
I believe Cassie Spiral CW.  :D

Alice

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #11 on: February 19, 2009, 06:34:21 pm »
Hi Tom's brother :D ;D (you guys are never going to live that down . . .) I think it's because on average the galaxies we see in GZ2 are nearer to us. One of the things you can just about see in my notes - which Cassie isn't covering up - is "redshift >1 hard to study", that is, bars aren't easily apparent if the galaxy is far away.

Warning - while you were typing a new reply has been posted. You may wish to review your post.

LOL Half! Awwwwwwwwww! ;D ;D ;D

Thomas J

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #12 on: February 19, 2009, 08:31:13 pm »
Great OOTD, Alice.  :) :)
I am very interested in the Universe- I am specialising in the Universe and all that surrounds it.....            Peter Cook.


EdV

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #13 on: February 19, 2009, 10:24:35 pm »
You know, it would be interesting to see what form of bar is more common at what redshift... that will help us understand what leads to what.
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jules

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Re: Thursday 19th February 2009: Barred Spirals and Bar Evolution
« Reply #14 on: February 20, 2009, 12:40:49 am »
Great OOTD Alice - even more research to think about!! :D