Over the next five years, our view of the Milky Way galaxy will be revolutionised by the European Space Agency's cornerstone Gaia mission. In particular, the 2nd Gaia data release (DR2) will be available from April 25 2018, and will contain astrometric and 3-band photometric data for around 1.4 billion sources across the whole sky, with a significant subset of these stars with radial velocity, extinction and effective temperature measurements. This will provide an unprecendented look at the stellar disc and halo of the Milky way.
To help understand and interpret these observations, we have generated synthetic stellar catalogues from our high-resolution simulations designed to match the volume, accuracy and data products provided by Gaia DR2.
This page contains information and documentation on how to use the catalogues, in addition to links to download the data, supplementary material such as gravitational potential grids, and example scripts that can be used to read and extract relevant data.
Mock catalogues from ab initio magneto-hydrodynamical simulations
We have generated mock catalogues for 6 high-resolution Auriga simulations: Au 6; Au 16; Au 21; Au 23; Au 24 and Au 27 (in the nomenclature of Grand et al. 2017). For each simulation, we compute mock catalogues for 4 different solar positions, each at a radius of 8 kpc and a height of 20 pc. The four azimuthal positions are distributed equally along the 8 kpc circle. Our fiducial azimuth is defined to be 30 degrees behind the major axis of the bar, in agreement with current estimates. As there are 4 equally distributed azimuth positions, there are 2 diametrically opposed mocks per halo at an angle of 30 degrees behind the bar.
For each solar position in each Auriga simulation, we compute 2 sets of mock catalogues:
- HITS mocks: generated using a modified version of the publicly available SNAPDRAGONS code (Hunt et al. 2015, MNRAS, 450, 2132)
- ICC mocks: generated using a method based on (Lowing et al. 2015, MNRAS, 446, 2274)
A description of the data fields and their units are given in the table below taken from the appendix of Grand et al. 2018 submitted.
Downloading the data
We have set up a querying system which accepts ADQL scripts and retrieves subsets of data. This can be accessed via this link, under the database name 'Grand2018a'. The table names are of the form [H|I]_AuXX_LY_AngleZZZ_[No]Ext where the I or H indicates ICC or HITS mocks, XX identifies the halo, Y is the resolution level (always 3 at the moment) and ZZZ is the orientation.
An example query to retrieve stars with G<13 mag within 5 kpc of the Sun for the fiducial HITS mock of halo Au 6 is:
Users are required to acquire a database account to use the system, which can be requested by filling in the form at the Virgo Database webpage.
3-dimensional force and potential grids
Three dimensional grids of the gravitational potential and forces for all 6 simulations. We have prepared a course, polar grid and a fine, cartesian grid that covers the central galaxy. The coarse polar grid 160 logarithmically spaced between 10 kpc and 300 kpc, with 300 and 150 bins in azimuth and latitude, respectively. The fine cartesian grid is of 21 kpc side-length with a spatial resolution of 125 pc (which is comparable to the softening length of the simulation).
The grids are available to download below:
A simple script to read the grids is provided here. In this script, one can see how the grids are read into the correct coordinates, and check the information on the units of the output.
Raw simulation snapshot data
We provide also snapshot data for Auriga 6, which is perhaps the most Milky Way-like of the Auriga galaxies (this file is about 3.5 GB). This snapshot is already oriented such that the Sun is located at the default mock position, and the (0,0,0) coordinate corresponds to the Galactic centre, not the Sun. The snapshot includes data such as positions, velocities, masses etc. for all the material inside the virial radius of the main halo, including dark matter particles, star particles, and gas cells. A summary of the data fields and units are given below: