Ananke: Gaia on FIRE

The Ananke framework (Sanderson et al 2019) generates realistic synthetic stellar surveys from cosmological baryonic simulations. We have used Ananke to create a set of synthetic phase-space surveys designed to resemble Data Release 2 of the Gaia astrometric survey from different solar viewpoints in the Latte suite of FIRE-2 simulations of Milky Way-mass galaxiesSanderson et al 2019 describes these synthetic surveys in detail.

Access the synthetic surveys on yt-hub:

View the list of columns

RGB flux map of a synthetic survey of m12f.
RGB flux map in galactic coordinates (|b|<50) of a synthetic survey of the FIRE-2 simulated galaxy m12f. Total flux in each of the three Gaia passbands was assigned to a different color channel, and the resulting image was median-filtered to diminish the effect of “hot” pixels caused by nearby stars.

We generated 3 synthetic surveys (each using different solar positions) from each of 3 Latte simulations, for a total of 9 synthetic surveys.

Each synthetic Gaia DR2-like survey features:

  • Cosmological formation histories with self-consistent dark-matter and gas accretion, satellite galaxies, and tidal streams/shells.
  • Spatially resolved stellar populations and young star clusters in realistically thin and dynamically complex star-forming disks. The Latte simulations provide sufficient resolution to model kinematically cold, single-age, mono-abundance stellar populations at mass resolution ~5000 Msun at z = 0, comparable to (massive) star clusters. Furthermore, the gas spatial resolution (as small as 1 pc) and temperature range (as cold as 10 K) resolve the formation of giant molecular clouds (GMCs) and the clustered formation of young stars inside of them.
  • Complete stellar populations synthesized using a Kroupa stellar initial mass function (IMF) and PARSEC model stellar isochrones.
  • Self-consistent dust extinction calculated using a constant dust-to-metals ratio, documented for easy adaptation to other extinction models. This provides realistic correlations between (young) stars and gas, including dust extinction near star-forming regions.
  • Simulated Gaia DR2-like uncertainties based on survey averages, with intrinsic values provided for use with more sophisticated error models.

The result is a self-consistent, dust-extincted synthetic survey of each simulated galaxy that leaves intact important observational relationships between gas, dust extinction, stellar populations, and dark matter.

Coming Soon: access through the NASA/IPAC Infrared Science Archive

Data model for Ananke synthetic Gaia DR2 surveys
Quantity Explanation Data type Unit
Fields with names identical to those in DR2
source_id Unique source identifier (per mock catalog) long
random_index Random index used to select subsets long
ra Right ascension double Angle (deg)
ra_error Standard error of right ascension double Angle (deg)
dec Declination double Angle (deg)
dec_error Standard error of declination double Angle (deg)
parallax Parallax double Angle (mas)
parallax_error Standard error of parallax double Angle (mas)
parallax_over_error Parallax divided by its error float
pmra Proper motion in RA direction double Angular Velocity (mas/year)
pmra_error Standard error of proper motion in RA direction double Angular Velocity (mas/year)
pmdec Proper motion in declination direction double Angular Velocity (mas/year)
pmdec_error Standard error of proper motion in declination direction double Angular Velocity (mas/year)
l Galactic longitude (converted from RA, dec) double Angle (deg)
b Galactic latitude (converted from RA, dec) double Angle (deg)
phot_g_mean_mag Extincted apparent G-band mean magnitude float Magnitude (mag)
phot_g_mean_mag_error Standard error of G-band mean magnitude float Magnitude (mag)
phot_bp_mean_mag Extincted apparent GBp-band mean magnitude float Magnitude (mag)
phot_bp_mean_mag_error Standard error of GBp-band mean magnitude float Magnitude (mag)
phot_rp_mean_mag Extincted apparent GRp band mean magnitude float Magnitude (mag)
phot_rp_mean_mag_error Standard error of GRp-band mean magnitude float Magnitude (mag)
bp_rp Reddened GBpGRp colour float Magnitude (mag)
bp_g Reddened GBpG colour float Magnitude (mag)
g_rp Reddened GGRp colour float Magnitude (mag)
a_g_val line-of-sight extinction in the G band, AG float Magnitude (mag)
e_bp_min_rp_val line-of-sight reddening E(GBp-GRp) float Magnitude (mag)
radial_velocity Radial velocity double Velocity (km/s)
radial_velocity_error Standard error of radial velocity a double Velocity (km/s)
Stellar Parametersb
teff_val Stellar effective temperature float Temperature (K)
lum_val Stellar luminosity float Luminosity (LSun)
Other fields not in the Gaia DR2 data model
parentid array index of the generating star particle in the snapshot file long
partid 0 if phase-space coordinates are identical to the generating star particle, 1 otherwise short
Phase space
ra_true true ra double Angle (deg)
dec_true true dec double Angle (deg)
rad_true true LSR-centric distance double Distance (kpc)
dmod_true true distance modulus double Magnitude (mag)
parallax_true true parallax double Angle (mas)
pmra_true true pm in ra direction double Angular Velocity (mas/yr)
pmdec_true true pm in dec direction double Angular Velocity (mas/yr)
radial_velocity_true true RV double Velocity (km/s)
l_true true Galactic long double Angle (deg)
b_true true Galactic lat double Angle (deg)
px_true, py_true, pz_true true position relative to LSRc double Distance(kpc)
vx_true, vy_true, vz_true true velocity relative to LSRc double Velocity (km/s)
phot_g_mean_mag_true true (i.e. after extinction, but before error convolution) apparent G-band mean magnitude float Magnitude (mag)
phot_bp_mean_mag_true true apparent GBp-band mean magnitude float Magnitude (mag)
phot_rp_mean_mag_true true apparent GRp-band mean magnitude float Magnitude (mag)
bp_rp_true true GBpGRp colour float Magnitude (mag)
bp_g_true true GBp– G colour float Magnitude (mag)
g_rp_true true G –GRp colour float Magnitude (mag)
phot_g_mean_mag_int intrinsic (i.e. before extinction or error convolution) apparent G-band magnitude float Magnitude (mag)
phot_bp_mean_mag_int intrinsic apparent GBp-band mean magnitude float Magnitude (mag)
phot_rp_mean_mag_int intrinsic apparent GRp-band mean magnitude float Magnitude (mag)
bp_rp_int intrinsic GBpGRp color float Magnitude (mag)
bp_g_int intrinsic GBp– G color float Magnitude (mag)
g_rp_int intrinsic G-GRp color float Magnitude (mag)
lognh log10 equivalent H column density along line of sight to star float cm-2
ebv E(B-V) reddening, calculated from equivalent NH float Magnitude (mag)
A0 A0, extinction at 550 nm, assuming RV=3.1 float Magnitude (mag)
Stellar Parameters
mact current stellar mass float Mass (Solar Mass)
mtip mass of a star at tip of giant branch for given age, metallicityd float Mass (Solar Mass)
mini stellar mass on zero-age main sequence float Mass (Solar Mass)
age log10 stellar age; identical for all stars generated from the same particle float Time (log yr)
logg surface gravity float Surface Gravity (log cgs)
feh [Fe/H] float Abundances (dex)
alpha [Mg/Fe] float Abundances (dex)
carbon [C/H] float Abundances (dex)
helium [He/H] float Abundances (dex)
nitrogen [N/H] float Abundances (dex)
sulphur [S/H] float Abundances (dex)
oxygen [O/H] float Abundances (dex)
silicon [Si/H] float Abundances (dex)
calcium [Ca/H] float Abundances (dex)
magnesium [Mg/H] float Abundances (dex)
neon [Ne/H] float Abundances (dex)

a. constant noise floor of 0.11 km/s added in quadrature
b. not error-convolved
c. see Sanderson et al. 2018 for a discussion of the coordinate systems
d. evolved stars are those with mact > mtip
e. all relative to solar; identical for all stars generated from the same particle.