How to access data of specifics galaxies in all snapshots?

Geferson Lucatelli
  • 29 May '15

Good evening, I'm Geferson Lucatelli, I'm was looking to the data/docs/api ,, and I see that it's possible download all data about galaxies/subhalos of the snapshot 135. But, I would like to know if it's possible to work with data of a specific galaxy/subhalo in all snapshots (of course that in snapshot 0 is difficult to have), then download this data. For example, I want do study how the galaxies evolve with time in the snapshots. I am student in physics bachelor's degree at the Universidade Federal do Rio Grande, Rio Grande do Sul, Brazil.

I know that it's possible to access this data by progenitors of a galaxy, but it is the only way to do it?


Geferson Lucatelli.

Dylan Nelson
  • 31 May '15

Hi Geferson,

For any subhalo ID at any snapshot, you can download a "cutout" of its particle data to work with.

If you want to see how a specific galaxy (or several specific galaxies) evolve in time, you need to use a merger tree to find a progenitor/descendant at some different snapshot, and this is what some of the examples do.

So no, you do not need to access this data using the progenitor, but to me this makes the most sense, if you are trying to follow the evolution of a galaxy.

Perhaps you can explain more what you would like to do, so I can give a better answer.

Geferson Lucatelli
  • 1
  • 1 Jun '15

Hi Dylan,

Yes, it's exactly this, thanks. I read about the "cutouts" and the "progenitors", and I understood well. Also, I got a script from API, and I added some lines, to select only this data, in order to be easily downloaded the progenitors/descendants of a subhalo/galaxy.

And I have another question. After I have the subhalos's data, how can I plot the data in visible light or in other wavelenghts?

Again, thank you.

Geferson L.

Dylan Nelson
  • 2 Jun '15

In general, calculating the emergent radiation of a subhalo in any given wavelength band can be quite complex, with many assumptions.

If you specifically mean for the stars, you may want to look at the GFM_StellarPhotometrics field for PartType4. This will give a very basic view of the stellar light output of each star particle (using a standard stellar population synthesis model).

Geferson Lucatelli
  • 3 Jun '15

Hello Dylan, Thank you, I will see it. I have a lot work to do.

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