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ProfileNathan
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Message 3523 - Posted: 27 May 2008, 19:18:30 UTC

I just started a search using data from SDSS stripe 82 which is the set of data we used in the paper we just got accepted to ApJ. This is a well studied piece of data that is along the Celestial Equator in the South Galactic Cap.

The Celestial Equator is an extension of the Earth's equator and defines the Equatorial Coordinate system seen below,

The piece of data can be seen below (the green strip) with respect to the rest of the SDSS survey.


What I'm looking at doing here is replicating the results seen in the paper before I move on to the rest of the data seen in the second image here.
~Nate~
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Message 3556 - Posted: 28 May 2008, 20:54:33 UTC - in response to Message 3523.  

I just started a search using data from SDSS stripe 82 which is the set of data we used in the paper we just got accepted to ApJ. This is a well studied piece of data that is along the Celestial Equator in the South Galactic Cap.

The Celestial Equator is an extension of the Earth's equator and defines the Equatorial Coordinate system seen below.


The graphics of the seach area is excellent! What made you decide to start with this area? Is there a particular area search that you want to cover for this upcoming run?
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ProfileNathan
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Message 3565 - Posted: 29 May 2008, 5:27:10 UTC

Thanks! I figured you guys would like to know a little more precisely where we're looking. I'll try and get a less ambiguous picture format to show where in relation to the rest of the Milkyway we're working.

We started with this specific piece of data because it is the best studied in regards to the Sagittarius Tidal Stream. Therefore, we would have a way to validate that we were getting the correct results when using non-simulated data. If we would have started with some other set of data, there would be no way to say it was correct, but at the same time not know it was incorrect either. Since we were able to replicate the results seen from previous work with smaller errors we were able to show that the method works and better than previous methods.

This is the first set of non-simulated data for Milkyway@home for the same reason. We need to show that we can replicate the results using BOINC on non-simulated data before we can move on to other data sets.

Once we have the results back from this first stripe, we then want to systematically cover the rest of the area seen in the second figure from my original post with similarly sized wedges. By doing this we'll be able to build up a complete image/map of the tidal stream, instead of just having a tiny piece of it. This will not be trivial though as there is obviously other structures present within the data that we either have to remove or simultaneously fit.
~Nate~
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Message 3566 - Posted: 29 May 2008, 8:09:39 UTC - in response to Message 3565.  

This is the first set of non-simulated data for Milkyway@home for the same reason. We need to show that we can replicate the results using BOINC on non-simulated data before we can move on to other data sets.

So... have all of the Work Units (WU's) thus far been in relation to a 'simulated' Milky Way galaxy?

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Cameron

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Message 3624 - Posted: 1 Jun 2008, 0:59:29 UTC

Well Thanks for the info. I can now visualise the wedges of work we've all been doing.
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Message 3629 - Posted: 1 Jun 2008, 8:10:06 UTC

THIS IS AWESOME

What are we searching for?
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Odysseus

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Message 3720 - Posted: 11 Jun 2008, 7:49:36 UTC - in response to Message 3629.  

What are we searching for?

AIUI we're not searching for anything, but modelling interactions between stars (or clusters or associations thereof) and comparing the results to observations of stellar distribution within our Galaxy.
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ProfileNathan
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Message 3815 - Posted: 17 Jun 2008, 16:35:38 UTC - in response to Message 3720.  

What are we searching for?

AIUI we're not searching for anything, but modelling interactions between stars (or clusters or associations thereof) and comparing the results to observations of stellar distribution within our Galaxy.


This is actually incorrect, we're not modeling interactions. We're actually not doing any "modeling" at all. What we are doing is looking for over-densities in the spatial data (positions of stars) that correspond to tidal disruptions of dwarf galaxies, specifically the Sagittarius Dwarf Galaxy (Sgr dSph) in this case.

With this data, the people that actually do do the modeling work will be matching their simulations to OUR RESULTS!

We are actually studying the observational data taken by the SDSS, so when you download a file called stars_82.txt or some similar things you are actually getting a list on coordinates for real objects in the sky!

~Nate~
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Message 3838 - Posted: 19 Jun 2008, 2:34:50 UTC
Last modified: 19 Jun 2008, 2:35:18 UTC

Hi Nate/Travis/Dave...was wondering why we haven't seen any more of these searches since the initial attempt failed and caused numerous errors. Have these errors been worked out yet and when will we be seeing more of these?

There is a run test applications option on everyones account page and I would be willing to help test to get a production version out.

Regards-Jeff
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ProfileNathan
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Message 3882 - Posted: 19 Jun 2008, 19:19:04 UTC - in response to Message 3838.  

I just started a new search today (about 20 minutes ago actually). The initial error caused a lot of bad WUs to need to get worked out and then we had an issue with the assimimilator. However, Travis has told me that things should be back to running smoothly now, and in response I started a search using the stripe 82 data. Hopefully I can get results back quickly, and we can move on to new data sets.
~Nate~
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ProfileNathan
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Message 3946 - Posted: 27 Jun 2008, 16:19:26 UTC

Figured I'd give you guys a heads up on the status of the searches and how they're doing.

In short, things are going great. There are a couple of things I need to get ironed out to make my life easier and to optimize the search space (the BOINC code uses a different optimization algorithm than what I previously used), but just with the two searches I've ran so far I can see that I can reproduce the results that we got in the ApJ paper! I'm not getting quite the accuracy I was getting before, but we expected this due to the optimization method we're using.

At any rate, this is great news! It shows that we can do real science using Milkyway@home and not just use simulated data sets!

Keep up the good work guys, and I'll be continuing to start new searches on new data sets, and I'll keep you updated as to when I start them and what they are.
~Nate~
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