Snapshots ouputs

Here, we provide a summary of the quantities written in the snapshots, in addition to positions, velocities, masses, smoothing lengths and particle IDs.

The tracer outputs are summarised on the Particle tracers page.

Sink particles

Name	Description	Units	Comments
NumberOfSinkSwallows	Number of merger events with other sinks	[-]
NumberOfGasSwallows	Number of gas particles accreted	[-]
TargetMass	Target mass required to spawn the next star particle	[U_M]	You can use it to determine if the target mass is so huge that the sink’s mass cannot spawn such a star. Such rare behaviour may bias the IMF towards high masses.
Nstars	Number of stars created by this sink	[-]
SwallowedAngularMomentum	Total angular momentum of accreted material	[U_M U_L^2 U_T^{-1}]
MetalMassFractions	Mass fraction of each tracked metal element	[-]	Only in GEAR chemistry module. Array of length N (number of elements), set at compile time via --with-chemistry=GEAR_N.
BirthScaleFactors	Scale factor at the time of sink creation	[-]	Only used in cosmological runs.
BirthTimes	Time when the sink was created	[U_T]	Only used in non-cosmological runs.
BirthDensities	Physical densities at the time of birth	[U_M U_L^{-3}]	Stored at birth time/redshift.
BirthTemperatures	Temperatures at the time of birth	[U_K]	Stored at birth time/redshift.
AccretionRates	Physical instantaneous accretion rates	[U_M U_T^{-1}]	At the current step
StarFormationRates	Star formation rates of the particles	[U_M U_T^{-1}]	If negative, stores last time/scale-factor at which gas was star-forming.

Stars

Name	Description	Units	Comments
BirthScaleFactors	Scale-factors when the stars were born	[-]	Only used in cosmological runs.
BirthTimes	Time when the stars were born	[U_T]	Only used in non-cosmological runs.
BirthMasses	Masses of the stars at birth time	[U_M]	SF and sinks modules
ProgenitorIDs	ID of the progenitor sinks or gas particles	[-]	SF and sinks modules
BirthDensities	Gas density at star formation	[U_M U_L^{-3}]	Only in SF module
BirthTemperatures	Gas temperature at star formation	[K]	Only in SF module
Potentials	Gravitational potential of the star	[U_L^2 U_T^{-2}]
StellarParticleType	Type of the stellar particle:	[-]	0: (discrete) single star 1: continuous IMF part star 2: single population star The last type corresponds to legacy IMF stars.
MetalMassFractions	Mass fraction of each metal element	[-]	Only in GEAR chemistry module. Array of length N (number of elements), set at compile time by --with-chemistry=GEAR_N.

Gas particles

Since hydro scheme writes its own set of outputs, we only provide the outputs that GEAR writes for gas particles.

Name	Description	Units	Comments
SmoothedMetalMassFractions	Mass fraction of each metal element smoothed over the SPH kernel	[-]	Only in GEAR chemistry module. Array of length N, set at compile time by --with-chemistry=GEAR_N
MetalMassFractions	Raw (non-smoothed) mass fraction of each metal element	[-]	Only in GEAR chemistry module. Same layout as above.
HI	Mass fraction of neutral H (\(\mathrm{H}\))	[-]	Only if GRACKLE_1 to 3
HII	Mass fraction of ionized H (\(\mathrm{H}^+\))	[-]	Only if GRACKLE_1 to 3
HeI	Mass fraction of neutral He (\(\mathrm{He}\))	[-]	Only if GRACKLE_1 to 3
HeII	Mass fraction of singly ionized He (\(\mathrm{He}^+\))	[-]	Only if GRACKLE_1 to 3
HeIII	Mass fraction of doubly ionized He (\(\mathrm{He}^{++}\))	[-]	Only if GRACKLE_1 to 3
e	Free electron mass fraction (\(\mathrm{e}^-\))	[-]	Only if GRACKLE_1 to 3
HM	Mass fraction of \(\mathrm{H}^-\)	[-]	Only if GRACKLE_2 or 3
H2I	Mass fraction of neutral \(\mathrm{H}_2\)	[-]	Only if GRACKLE_2 or 3
H2II	Mass fraction of ionized \(\mathrm{H}_2^+\)	[-]	Only if GRACKLE_2 or 3
DI	Mass fraction of neutral D (\(\mathrm{D}\))	[-]	Only if GRACKLE_3
DII	Mass fraction of ionized D (\(\mathrm{D}^+\))	[-]	Only if GRACKLE_3
HDI	Mass fraction of \(\mathrm{HD}\)	[-]	Only if GRACKLE_3