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# System prepended metadata

title: Latte simulations

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# Latte simulations


## AHF subhalo catalogues

| Galaxy  | m12f  |  m12i  | m12m  | 
|---|---|---|---|
| # subhalos with N>85  | 1298 |  1001 | 1281  |
| # subhalos with N>85 & r<100 kpc  |  230 |  285 | 278  |
| # subhalos (removing dwarfs) with N>85 & r<100 kpc  | 226  |  279 | 269  |

The condition for removing dwarfs is as follows:
- We calculate the relative velocity between each star situated within 1 kpc from the center of a subhalo.
- If the relative velocity is smaller than the escape speed (calculated assuming point mass approximation), then the halo-associated star is said to be bound to the subhalo.
- We remove all subhalos that have more than 1 bounded star.

The following plot shows the relative velocity between halo-associated stars and their associated subhalo as a function of subhalo escape velocity. The latter velocity is calculated under the point masss approximation.
![](https://i.imgur.com/SFua3UP.png)
We would like to understand a bit more about the bounded stars (halo-associated stars satisfying $V_{\rm diff}<V_{\rm esc}$), so in the following we show the fraction of halo-associated stars that are bounded to a subhalo as a function of subhalo mass. The color bar shows the number of stars bounded to given subhalo.
![](https://i.imgur.com/JRJxwvd.png)

# What is the cause of the difference in performance between Latte and Synthetic Gaia?

## Sampling generation
From a given star particle in the Latte simulation, a population of synthetic stars is created. Each of these synthetic stars are sample from the phase-space position of the parent Latte star particle. In this way, a smearing scale is introduced in the synthetic survey. Thus, washing out the kinematic signature that dark subhalos leave in the stars.

From [Sanderson et al](https://ui.adsabs.harvard.edu/abs/2020ApJS..246....6S/abstract) it is not clear what are the smearing scales. For this reason, we define these scales in position and velocity as following.

For the ${\tt m12f}$ galaxy and LSR0, we show in the following plot the distribution of difference in x, y and z positions between each halo-associated synthetic star position and the true position of its corresponding parent star particle. We then define the smearing scale in position as the standard deviation of these distributions which is roughly 0.7 kpc in each of the directions.
![](https://i.imgur.com/vo5fubT.png)

The same but for velocities. The standard deviation is roughly 10 km/s in each of the axes.
![](https://i.imgur.com/1V0fahT.png)







