Best-fitting Sgr disruption models


These are the simulation file results for the Law and Majewski (2010) model of Sgr orbiting in a triaxial Galactic potential. Note that this model supercedes the previous models of LJM05.

The first file, SgrTriax_DYN.dat.gz consists of 26 columns of data as given below. These columns generally describe the positions and motions of the 10^5 individual simulation particles. All distances are in kpc, all velocities in km/s, all angular measurements are in degrees, and all proper motions are in mas/yr.
  1. Lambda_sun: orbital longitude.
  2. Beta_sun: orbital latitude
  3. RA: Right ascension
  4. Dec: Declination
  5. l: Galactic longitude.
  6. b: Galactic latitude.
  7. X_GC: Standard left-handed Galactocentric Cartesian coordinate.
  8. Y_GC: Standard left-handed Galactocentric Cartesian coordinate.
  9. Z_GC: Standard left-handed Galactocentric Cartesian coordinate.
  10. X_sun: Right-handed heliocentric Cartesian coordinate in the Lambda_sun system.
  11. Y_sun: Right-handed heliocentric Cartesian coordinate in the Lambda_sun system.
  12. Z_sun: Right-handed heliocentric Cartesian coordinate in the Lambda_sun system.
  13. X4: Right-handed heliocentric Cartesian coordinate in the Lambda4 system.
  14. Y4: Right-handed Galactocentric Cartesian coordinate in the Lambda4 system.
  15. Z4: Right-handed Galactocentric Cartesian coordinate in the Lambda4 system.
  16. U: Galactic U velocity (d(X_GC)/dt).
  17. V: Galactic V velocity (d(Y_GC)/dt).
  18. W: Galactic W velocity (d(Z_GC)/dt).
  19. d: Heliocentric distance.
  20. vgsr: Radial velocity relative to the Galactic Standard of Rest (NB: GSR, not LSR).
  21. mu_l cos(b): Proper along galactic longitude, heliocentric frame
  22. mu_b: Proper motion along galactic latitude, heliocentric frame
  23. mu_alpha cos(delta): Proper motion along right ascension, heliocentric frame
  24. mu_delta: Proper motion along declination, heliocentric frame
  25. Pcol: "Color", or unbound era of simulated particle
  26. Lmflag: -1 for trailing arm debris, +1 for leading arm debris

The younger segments of tidal debris are constrained to match the 2MASS/SDSS observations, while the older segments should be regarded as predictions for where tidal debris might be expected if it extends beyond that currently traced by 2MASS/SDSS. The dynamical 'age' of a particle is given by the parameter 'Pcol', which indicates the pericentric passage on which the particle became unbound from Sgr. Values of Pcol=-1 indicate debris which is still bound at the present day, Pcol=0 indicates debris stripped on the most recent pericentric passage of Sgr, Pcol=1 indicates debris stripped on the previous pericentric passage, etc. This corresponds to the 'point color' used in plots by LM10 color-coding debris from different pericentric passages as different colors. Black points: Pcol=-1, orange points: Pcol=0/1, magenta points: Pcol=2/3, cyan points: Pcol=4/5, green points: Pcol=6/7. Roughly speaking, values of Pcol<=3 best correspond to tidal debris observed in 2MASS/SDSS. See LM10 for further details.

The Sgr streams wrap entirely around the Galaxy, and as such overlap themselves in angular coordinates along the stream. To facilitate separation of younger from older wraps, the parameter 'Lmflag' specifies in which wrap a given particle is located. Lmflag = +1/+2 corresponds to the first/second wrap of the leading stream respectively, Lmflag = -1/-2 corresponds to the first/second wraps of the trailing stream respectively. See Fig 8 of LM10.

Simulations are realized using 10^5 particles in a self-consistent field code.

The second file, SgrTriax_FEH.dat.gz consists of 8 columns of data as given below. These columns generally describe the stellar population 'tagging' assigned to individual particles. Each row in the second file directly corresponds to the matching row in the first file. I.e., row 7 of SgrTriax_FEH.dat corresponds to row 7 of SgrTriax_DYN.dat, etc.
  1. E*: Order-sorted internal energy (kinematic+potential) in the initial satellite (see LM10).
  2. Popn: Stellar population to which each particles is assigned
  3. FeH: Metallicity [Fe/H]
  4. Age: Age in Gyr
  5. tubBP: Time before present (in Gyr) at which particle became unbound from Sgr
  6. JminK: J-K color assigned
  7. Kabs: Absolute K magnitude
  8. Kapp: Apparent K magnitude
The third file, SgrTriax_orbit.dat, gives the orbital history as a function of time of the Sgr dwarf core in the adopted model. This data file consists of the following columns.
  1. Time (Gyr)
  2. Lambda_sun: orbital longitude.
  3. Beta_sun: orbital latitude
  4. RA: Right ascension
  5. Dec: Declination
  6. X_sun: Right-handed heliocentric Cartesian coordinate in the Lambda_sun system.
  7. Y_sun: Right-handed heliocentric Cartesian coordinate in the Lambda_sun system.
  8. Z_sun: Right-handed heliocentric Cartesian coordinate in the Lambda_sun system.
  9. X_GC: Standard left-handed Galactocentric Cartesian coordinate.
  10. Y_GC: Standard left-handed Galactocentric Cartesian coordinate.
  11. Z_GC: Standard left-handed Galactocentric Cartesian coordinate.
  12. d: Heliocentric distance.
  13. vgsr: Radial velocity relative to the Galactic Standard of Rest (NB: GSR, not LSR).
Negative time values represents the past (trailing) path of Sgr, positive time the future (leading) path. The total interaction time of Sgr was arbitrarily chosen to be 8 Gyr.
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