1. Spherical Halo
2. Evolving and static streams
3. The Sagittarius Stream
4. The Palomar 5 Stream
5. The Via Lactea Streams
6. Aquarius Challenge
7. Gas-dynamical Challenge
8. Finding Streams Challenge
9. Progenitor DM profile and halo properties (2015!)

Update 30 October 2014: fixed coordinate transformation to observables. Now consistent with, and uses same parameters as, Kester Smith's Java applet. If you downloaded earlier than Oct 30, re-download

This test aims to identify how Gaia-like errors and the number of streams available affect the ability of various codes to recover the potential. The challenge is to take one or more of the data sets below and report the results of your fitting code as one or more measurements of the enclosed mass of the host halo as a function of radius.

The streams are from the mock stellar halo described in Section 3.2 of Sanderson, Helmi, & Hogg (2014). The progenitors are chosen from a distribution intended to mimic the present-day Milky Way satellites; stars are integrated as test particles in the isochrone potential given in the paper.

The challenge has two parts, and hence two associated data sets: one with Gaia-like errors, and one with errors including ground-based follow-up from planned spectroscopic surveys. In each case the stellar positions & velocities have been convolved using an error model. Only stars with complete 6D phase space information are included in the set (denoted by the tag dq). Since this selects a different subset of stars from the halo depending on the error model, each data set includes the error-convolved coordinates in one group of files (denoted by the tag cxv), and the pre-convolution coordinates for the same set of stars in another group of files (denoted by the tag txv).

For each part both the full stellar halo (all 153 progenitors) and a subset of 20 progenitors (with more than 100 stars each) are provided. The same 20 progenitors are used as the subset for each of the two error models. To test on a single stream, use the first stream in the 20-progenitor subset (id #26). Each progenitor's stars' coordinates (x,y,z,vx,vy,vz) are provided in a separate text file tagged with the progenitor's ID number. These are in Galactocentric Cartesian coordinates with distances in kpc and velocities in km/s.

Click to download.

• SphericalIsochrone.GaiaOnly.All.tgz — entire stellar halo convolved with Gaia errors. The 6 columns are x,y,z,vx,vy,vz. Positions in kpc, velocities in km/s.
  • *.txv.* are xv before error convolution
  • *.cxv.* are xv after error convolution
  • *.obs.* are convolved observable coordinates and error bars. The 11 columns are: apparent V magnitude, RA, dec, parallax, parallax error, proper motion in RA, PM_{RA} error, PM in dec, PM_{dec} error, RV, RV error.
• SphericalIsochrone.GaiaOnly.20streams.tgz — subset of 20 streams convolved with Gaia errors, same naming convention/columns as above
• SphericalIsochrone.GaiaOnly.subsample.tgz — for exploratory plotting purposes, two files containing 1/20th of the stars in each progenitor with full 6D coordinates, concatenated into one big list (~10MB), with (.cxv) and without (.txv) errors.
• SphericalIsochone.GaiaOnly.sub.info — for each progenitor, lists the ID number, number of stars with full measured 6D positions (i.e. the number of rows in each of the data files in .All and .20streams), and number included in .subsample.
• SphericalIsochrone.progs.info — information about the progenitors of the streams: ID#, *total* number of [RGB] stars in the original progenitor, time since infall in Myr, log luminosity in solar units, log *total* mass (stars+dark matter) in solar masses, scale radius in kpc, velocity dispersion in km/s, orbital apocenter radius in kpc, and orbital circularity [=L/L_circ(E)].

• SphericalIsochrone.GaiaGround.All.tgz — entire stellar halo including ground-based radial velocities
• SphericalIsochrone.GaiaGround.20streams.tgz— subset of 20 streams of the above
• SphericalIsochone.GaiaGround.subsample.tgz — 1/20th subsample for the data set including ground-based RVs
• SphericalIsochone.GaiaGround.sub.info — same as above for this data set
• SphericalIsochrone.progs.info — same file as in the other tarball

Please do not use the mock halo data for purposes other than testing potential-fitting codes without asking Robyn first. Thanks for your understanding!

When making use of this data, please cite the Gaia Challenge Wiki and Sanderson, Helmi, & Hogg 2014, ApJ subm., arXiv:1404.6534.

Good luck!

Update 30 October 2014: new format and errors convoluted with Robyn's code.

This test is aimed at understanding the effect that time-evolution of the galactic potential can have on the different potential recovery methods. The challenge is to use the datasets below, which contain a set of streams evolved in both a static and an evolving potential. They were made with approximately the same action distribution and result in very similar streams. The most striking differences are that the length of the stream is different between the evolving and static case, and that the stream-orbit misalignment is different.

The potential for these streams is based http://arxiv.org/abs/1401.5797. For the cosmologically motivated growth, we used an NFW potential with $\Omega_m = 0.29$, $\Omega_m + \Omega_\Lambda = 1.0$, $h_{100} = 0.71$ and an inside-out growth pattern set by $a_g = 0.8$, $\gamma=2$. At the final time, the potential is set by $r_s=12$ kpc and $M_s = 5 \times 10^{11} M_\odot$.

As in Robyn's data, in each case the stellar positions & velocities have been convolved using an error model. Only stars with complete 6D phase space information are included in the set (denoted by the tag dq). Since this selects a different subset of stars from the halo depending on the error model, each data set includes the error-convolved coordinates in one group of files (denoted by the tag cxv), and the pre-convolution coordinates for the same set of stars in another group of files (denoted by the tag txv).

Each progenitor's stars' coordinates (x,y,z,vx,vy,vz) are provided in a separate text file tagged with a stream ID number from 1 to 15. These are in Galactocentric Cartesian coordinates with distances in kpc and velocities in km/s.

Click to download

SphericalNFW.org.zip — original test-particle simulation without errors or selection; contains both streams in an evolving and in a static potential (tag evol and tag stat). Positions in kpc, velocities in kpc/Gyr.

SphericalNFW.stat.dq.tgz — The sample of streams in the static potential convolved with Gaia errors and selected for visibility with GAIA. The 6 columns are x,y,z,vx,vy,vz. Positions in kpc, velocities in km/s.

SphericalNFW.evol.dq.tgz — As above for the streams in the evolving potential.

SphericalNFW.stat.intermed.dq.tgz — Error-convolved observed coordinates and error bars for all the streams (cobs tag). The 11 columns are apparent V magnitude, RA, dec, parallax, parallax error, proper motion in RA, PM_{RA} error, PM in dec, PM_{dec} error, RV, RV error. Also contains the sample of streams in the static potential convolved with Gaia errors (cxv tag). Again, the 6 columns are x,y,z,vx,vy,vz. Positions in kpc, velocities in km/s.

SphericalNFW.evol.intermed.dq.tgz — as above for the evolving potential.

I thank Robyn Sanderson for kindly making the error convolved data available.

When making use of data in this part of the challenge, please cite the Gaia Challenge Wiki; http://arxiv.org/abs/1401.5797 (potential evolution model) or Buist et al. (in prep, streams in a time-evolving potential). Contact Hans for questions: buist@astro.rug.nl

Included in this challenge are particles selected from the Law & Majewski (2010; LM10) simulation of satellite disruption along an orbit similar to the Sagittarius (Sgr) dwarf galaxy. The goal of this challenge is to use present-day, 6D kinematic information for some sample of Sgr stream stars in conjunction with the orbit of the progenitor system to infer the potential used in the simulation. Download the challenge here. Contact Adrian for questions: adrn@astro.columbia.edu

Assume we know the position and velocity of the Sgr progenitor perfectly:

X,Y,Z = (19.788, 2.396, -5.848) kpc

U,V,W = (224.707, -35.254, 196.671) km/s

LM10 take Vlsr = 220 km/s, Rsun = 8 kpc.

All positions are in kpc, velocities in km/s, proper motions in mas/yr, angles in degrees.

sgr.subsample_pure_gaia.txt: This file contains positions (observable and cartesian) for 100 stars, selected uniformly from the first leading/trailing wraps of the Sgr stream (dark crosses in sgr.selected_stars.png). We imagine that these stars are RR Lyrae in the stream. The positions and velocities have been ‘observed’ assuming Gaia proper-motion errors, photometric distance errors (~15%), and 20 km/s radial velocity errors, typical for RR Lyrae.

sgr.subsample_gaia_spitzer.txt: This file contains positions (observable and cartesian) for 100 stars selected uniformly from the first leading/trailing wraps of the Sgr stream (dark crosses in sgr.selected_stars.png). Now, instead of 15% distance errors, we assume we can get 2% distance measurements to these stars using the mid-IR period-luminosity relation for RR Lyrae (see Madore & Freedman 2012, ApJ, 744, 132).

The positions and velocities have been ‘observed’ assuming Gaia proper-motion errors, mid-IR PL distance errors (2%), and 20 km/s radial velocity errors typical for RR Lyrae.

sgr.all_particles.txt: Also included are the true positions and velocities of all (36,928) particles in the first leading/trailing wraps. You can use these with your own error estimates if you’d like.

When making use of data in this part of the challenge, please cite the Gaia Challenge Wiki; Law & Majewski, 2010, ApJ, 714, 229; and Price-Whelan et al., in prep.

Here's the link to the github repository of the paper: https://github.com/ahwkuepper/pal5challenge

This part of the challenge focuses on a cold stellar stream produced by a low-mass globular cluster. For this purpose, an N-body model of the outer-halo Milky Way cluster Palomar 5 is provided. It has been evolved for 4 Gyr in an analytic Milky Way-like potential using a modified version of the direct N-body code NBODY6 (see Aarseth, 2003, Gravitational N-Body Simulations, Cambridge University Press). Download the updated challenge here. Contact Andreas for questions: akuepper@astro.columbia.edu

Given perfect information on the positions and velocities of all Palomar 5 members, how well can the underlying potential be determined? This is basically as good as it gets. From this ideal case, more realistic and tougher challenges can be constructed by reducing the sample size, reducing phase-space information, adding errors and adding contaminants.

An interesting question is also the influence of the choice of solar parameters on the results (i.e. Galactocentric distance, LSR velocity, etc.). The assumed values are given below.

How does Gaia help us with determining Pal 5's orbit? Get the model data file convolved with the Gaia error model here. The proper motions in galactic coordinates and the radial velocities have been modified and the estimated Gaia errors are attached as two new columns to the right.

The file Pal5_4k.txt contains all 65,356 particles of the N-body model of Palomar 5 and its tidal tails. The columns are described in the header of the file. They give Cartesian coordinates and observables for positions and velocities of all particles. All numbers are either in pc and km/s, or degree and mas/yr, respectively.

The Cartesian coordinates are given in the Galactic rest frame. The observables were derived assuming a solar Galactocentric distance of 8.33 kpc and a LSR motion of 239.5 km/s (Gillessen et al., 2009, ApJ, 692, 1075). In addition, the solar reflex motion was assumed to be (11.1, 12.24, 7.25) km/s (Schönrich et al., 2010, MNRAS, 403, 1829).

The present-day position of Palomar 5 is RA = 229.022083 deg, Dec = -0.111389 deg or l = 0.852059 deg, b = 45.859989 deg, respectively. The present-day Cartesian coordinates of the progenitor are

• x = 7816.082584 pc
• y = 240.023507 pc
• z = 16640.055966 pc
• vx = -37.456858 km/s
• vy = -151.794112 km/s
• vz = -21.609662 km/s

The Gaia uncertainties mess up the radial velocities and proper motions of the stream stars, but maybe the sheer number of stars can help us here.

• $M_{Halo} = 1.81194\times 10^{12}\,M_{\odot}$
• $r_{Halo} = 32260\,pc$
• $q_z = 0.8140$
• $M_{Pal5}(t=-4 Gyr) = 31090\,M_{\odot}$
• $M_{Pal5}(t=today) = 13150\,M_{\odot}$
• $d_{Sun} = 23190\,pc$
• $V_C(r_{Sun}) = 249.01\,km/s$
• $V_C(r_{Pal5}) = 247.84\,km/s$
• $V_C(r_{Halo}) = 251.99\,km/s$
• $a(r_{Sun}, 0, 0) = 7.95\,pc/Myr^2$
• $a(r_{Pal5}) = a(7816 pc, 240 pc, 16640 pc) = 3.51\,pc/Myr^2$
• $a(r_{Halo}, 0, 0) = 2.06\,pc/Myr^2$

Flattened NFW halo:

• $\Phi_{Halo}(R, z) = -\frac{GM}{\sqrt{R^2+\frac{z^2}{q_z^2}}}\ln\left(1+\frac{\sqrt{R^2+\frac{z^2}{q_z^2}}}{r_{Halo}} \right)$

Jaffe bulge:

• $\Phi_{Bulge}® = \frac{GM_{Bulge}}{b_{bulge}}\ln{\frac{r}{r+b_{bulge}}$
• $M_{Bulge} = 3.4\times 10^{10}\,M_\odot$
• $b_{Bulge} = 700.0\,pc$

Miyamoto-Nagai disk:

• $\Phi_{Disk}® = -\frac{GM_{Disk}}{\sqrt{R^2+\left(a_{Disk}+\sqrt{z^2+b_{Disk}^2}\right)^2}}$
• $M_{Disk} = 1.0\times 10^{11}\,M_{\odot}$
• $a_{Disk} = 6500\,pc$
• $b_{Disk} = 260\,pc$

When making use of data in this part of the challenge, please cite the Gaia Challenge Wiki; and Küpper et al., in prep.

This final part of the challenge consists of cold stellar streams evolved in the Via Lactea II (VL2) potential. Via Lactea, a pure dark matter N-body simulation, resembles a Milky Way-sized dark matter halo with about 10% of the mass being in subhaloes at z=0 (see Diemand et al., 2008, Nature, 454, 735 for more details). The streams were generated in a re-simulation of the final 6 Gyr of the original VL2 computation using the streakline method described in Küpper et al., 2012, MNRAS, 420, 2700. Download the challenge here. Contact Ana for questions: ana.bonaca@yale.edu

This part of the challenge comes in two parts:

1. What is the best-fit potential of the VL2 at z=0 given a certain stream?

2. Assuming Gaia uncertainties for positions and velocities of stream stars, how does the confidence in best-fit potential parameters depend on the stream distance from the observer?

Provided are current positions and velocities of four streams with Palomar 5-like progenitors, which have been grown and evolved for 6 Gyr in VL2. The data files (vl2.streamN.dat) contain six columns: x (kpc), y (kpc), z (kpc), vx (km/s), vy (km/s), vz (km/s). All coordinates are in the Galactocentric system. Each file has 12,001 lines: the first line is the current position of the progenitor, lines 2-6,001 give the positions of leading tail stars, while lines 6,002-12,001 give the positions of trailing tail stars.

A list of 100,000 dark matter particle positions and velocities in the final VL2 snapshot: http://www.ucolick.org/~diemand/vl2/data/vl2subset_relposvel.txt . Particle mass of 2.823e7 Msun will give the correct scaling of the total halo mass.

When making use of data in this part of the challenge, please cite the Gaia Challenge Wiki; Diemand et al., 2008, Nature, 454, 735; and Bonaca et al. (2014)

(Last update: 28/Aug/2015)

What can you learn about a galaxy's potential/mass profile from its stellar halo? This is a very broad challenge in which we want to know how well various codes work on actual N-body simulation data. In this case the potentials no longer have simple analytical forms and evolve throughout the simulation. The stellar haloes are made up of satellites that are in various stages of disruption: some are still identifiable as streams and others will have been completely destroyed.

The dataset is based on a dark matter N-body simulation populated with stars. The simulation used is the Aquarius A halo (Springel et al. 2008). The Cooper et al 2010 method has been used to populate the halo with stars. This uses the semi-analytical model Galform to predict star formation occurring in each subhalo. The stellar mass is then tagged onto the most bound 1% dark matter particles in the corresponding haloes in the N-body simulation at the appropriate times. These tagged dark matter particles can be located in the final snapshot to track where the stellar mass ends up.

10 streams extracted from the Aquarius A-2 simulation. These have been visually selected as extended, coherent objects in the process of disruption. Each stream is made up by a random subset of the particles that were once a member of the progenitor satellite. In each case while the majority of particles will either be in the satellite or in the stream structure, however, a notable fraction may be completely disassociated.

The Sun has been placed at 8 kpc with a velocity of (0,220,0)km/s, All positions/velocities are then given in heliocentric coordinates and the x axis points towards the galactic centre (8,0,0) kpc. All files are in ASCII, with the first line giving the number of objects in the file. The following data files are available:

AquariusA2streams.ne.dat - Positions and velocities of particles in the 10 streams without errors. The 14 columns are position x, y, z (in kpc), galactic coordinates l, b, (radians), parallax (muas), velocity v_x, v_y, v_z (in km/s), proper motions mu_l, mu_b (in muas/yr), radial velocity (km/s), flag to indicate whether bound to subhalo or not (bound==1, unbound==0), stream ID.

AquariusA2streams.dat - Observable quantities including Gaia errors (generated using PyGaia). The 8 columns are apparent G-band magnitude, parallax (muas), parallax error, proper motions mu_l, mu_b (in muas/yr), proper motion error, radial velocity (km/s), radial velocity error.

Streams have been populated with one red KIII giant per 40 solar masses (Helmi et al. 2011; Marigo et al. 2008), with M_V = 1, V-I = 1. The sample includes stars with G band > 20, which would be outside of the Gaia limits. Removing these stars eliminates several of the streams.

This is the whole stellar halo catalogue based on the Aquarius A-2 simulation. Details about how the catalogue is constructed can be found in Cooper et al. (2010). The catalogue includes all the accreted particles in the stellar halo. It is the parent catalogue used to make the 10 streams in the stream catalogue above. Again the Sun has been placed at 8 kpc with a velocity of (0,220,0)km/s, All positions/velocities are given in heliocentric coordinates. Files are in ASCII format, with the first line giving the number of objects in the file. Notice each object, instead of being a single star, is a particle that represents a single stellar population. The following data files are available:

AquariusA2halostars.ne.dat - Positions and velocities of particles in the stellar halo without errors. The 18 columns are position x, y, z (in kpc), galactic coordinates l, b, (radians), parallax (muas), velocity v_x, v_y, v_z (in km/s), proper motions mu_l, mu_b (in muas/yr), radial velocity (km/s), mass (Msun/h), age (Gyr), metallicity, potential at the current particle position formed by all the dark matter particles in the FoF group of the simulation ((km/s)^2), flag to indicate whether bound to subhalo or not (bound==1, unbound==0), stream ID. All particles share the same stream ID comes from the same satellite, and thus the stream ID can be used to identify streams.

AquariusA2halostars.dat - Observable quantities including Gaia errors (generated using PyGaia). The 7 columns are apparent parallax (muas), parallax error, proper motions mu_l, mu_b (in muas/yr), proper motion error, radial velocity (km/s), radial velocity error.

Each particle in the halo star catalogue above represents a stellar population instead of individual stars. We have further sampled these particles into individual stars and details about the sampling can be found in Lowing et al. (2014). A complete mock catalogue containing all the stars in the accreted stellar halo is available at http://galaxy-catalogue.dur.ac.uk:8080/StellarHalo, as a public SQL database. This catalogue contains useful observed properties of stars such as their magnitudes in five SDSS bands and effective temperature.

(NEW-Aug 2015)

These are Gaia observable K giant and RR Lyrae stars from the Aquarius A2 halo, extracted from the Lowing et al. 2015 mock catalogues explained in the previous subsection.

Error prescriptions: Proper motion and radial velocity errors have been simulated with Gaia error prescriptions as of Jun-2015 in Merce Romero’s Gaia error code. Photometric distance errors of 20% and 7% have been simulated for K giants and RR Lyrae stars respectively (these precisions are achievable using Gaia data for photometric distance measurements). The simulation of observables includes the effect of extinction, based on the 3D reddennig map from Drimmel et al. (2003). The Sun has been placed at X=8 kpc with a velocity of (0,220,0)km/s.

The SQL queries used to extract the stars are provided as part of each file’s header. The following ASCII files are available:

• AquariusA2_KIII.gerr.dat.gz - (91Mb) K-giants catalogue
• AquariusA2_RRLS.gerr.dat.gz - (20Mb) RR Lyrae catalogue
  • Catalogue file structure:
    • Av, V, Gmag, Grvs : V-band extinction, V-band, G and Grvs apparent magnitudes
    • xX,xY,xZ,xVX,xVY,xVZ : error-free cartesian galactocentric coordinates (kpc) and velocities (km/s)
    • xl_deg,xb_deg,xRhel_kpc,xmulcosb_masyr,xmub_masyr,xvrad : error-free observables (l,b, heliocentric distance in kpc, proper motions in mas/yr, radial velocities in km/s)
    • gX,gY,gZ,gVX,gVY,gVZ : error-convolved cartesian galactocentric coordinates and velocities.
    • gl_deg,gb_deg,gRhel_kpc,gmulcosb_masyr,gmub_masyr,xvrad : error-convolved observables
    • IDstream: progenitor ID. Stars with same IDstream come were accreted in the same progenitor.
• AquariusA2.progenitor.tracer.info
  • Progenitor info file structure:
    • IDstream, TreeID: progenitor ID, TreeID (Aquarius native progenitor ID)
    • infallZ,StellarMass,mlogage_yr,mZmetal : progenitor's infall redshift, total stellar Mass, mean log(age) and mean metallicity of stellar population
    • NKIII_all, NKIII_G20 : total number and Gaia observable (G<20) number of K giants stars in progenitor
    • NRRLS_all, NRRLS_G20 : total number and Gaia observable (G<20) number of RR Lyrae stars in progenitor

These are provisional files provided for Gaia Challenge purposes (potential fitting and stream finding challenges). The final set for all five haloes will be published in Mateu et al. in prep and made available as part of the public Aquarius SQL Database.

We also provide analogous catalogues for Andreea Font's LJMU Gas-Dynamical Simulations (see Gas-dynamical Challenge).

The full phase space distribution of a tracer population bound to an idealized dark matter halo potential can be obtained from the Eddington formula, assuming a particular parameterization of the distribution function (DF). We have approximated the potential of Aquairus halo A using a spherical NFW fit to its dark matter density profile and randomly sampled N points from a corresponding DF having two integrals of motion (binding energy and angular momentum), assuming a simple form for the tracer density and velocity anisotropy. Five random realizations can be downloaded here [fel1.dat,fel2.dat,fel3.dat,fel4.dat,fel5.dat]. Meanings of the 11 columns are radius (kpc), theta, phi (two position angles in units of radians), radial velocity (km/s), tangential velocity (km/s), x, y,z (kpc), vx, vy, vz (km/s)

There are six parameters in the distribution function: three spatial parameters that determine the spherically symmetric density profile of tracers, two parameters determine the NFW potential and one parameter for the velocity anisotropy of tracers. To generate the distribution, we assume the radial profile of tracers is a double power law form

<latex>

  $\rho(r)\propto \frac{1}{(\frac{r}{r_0})^\alpha+(\frac{r}{r_0})^\gamma}$

</latex>

with

<latex>

  $r_0=69.014\mathrm{kpc}$

</latex>

<latex>

  $\alpha=2.301$

</latex>

<latex>

  $\gamma=7.467$.

</latex>

The velocity anisotropy of tracers is adopted to be

<latex>

  $\beta=0.715$.

</latex>

The two parameters that determines the NFW potential are chosen to be the true values for Aquarius A

<latex>

  $r_s=15.2\mathrm{kpc}$

</latex>

and

<latex>

  $\rho_s=10^{7.34}M_\odot/\mathrm{kpc}^3$.

</latex>

Additional information is available about the halo, including the dark matter particle data, subhalo catalogues and data based on the other Aquarius haloes. Contact us for questions: bilinxing.wenting@gmail.com, a.p.cooper@durham.ac.uk, b.j.lowing@durham.ac.uk

For information about the Gaia-error-convolved mock catalogues for KIII and RRLyrae stars contact: cmateu@astrosen.unam.mx

When making use of data in this part of the challenge, please cite the Gaia Challenge Wiki. Please cite Cooper et al.(2010) for the stream catalogue and the halo star catlaogue. Cite Lowing et al. (2014). for the complete mock catalogue of individual halo stars. The error-convolved mock catalogues (K-giants and RR Lyraes) will be described in Mateu et al. in prep. The sample of tracers obeying the Eddington formula will be described in Wang et al. in prep.

(Latest update: 28/Aug/2015)

Use a series of gas-dynamical simulations of Milky Way-type galaxies to retrieve the potential.

Here are two mock catalogues for K giant stars in two Haloes from Andreea Font's LJMU Gas-Dynamical simulations (Font et al. in prep). We have used the same methods as for the Error-convolved mock catalogue of individual halo stellar tracers: i.e. Ben Lowing's code (2015) to resample star particles into individual stars, Xue et al. (2014) criteria to select K giant stars and the same error prescriptions (described below).

Error prescriptions: Proper motion and radial velocity errors have been simulated with Gaia error prescriptions as of Jun-2015 in Merce Romero’s Gaia error code. Photometric distance errors of 20% have been simulated for K giants (e.g. Xue et al. 2014). The simulation of observables includes the effect of extinction, based on the 3D reddennig map from Drimmel et al. (2003). The Sun has been placed at X=8 kpc with a velocity of (0,220,0)km/s.

The SQL queries used to extract the stars are provided as part of each file’s header. The following ASCII files are available:

• LJMU001_KIII.gerr.dat.gz - (380Mb) K-giants catalogue for LJMU Halo 001
• LJMU006_KIII.gerr.dat.gz - (160Mb) K-giants catalogue for LJMU Halo 006
  • Catalogue file structure:
    • Av, V, Gmag, Grvs : V-band extinction, V-band, G and Grvs apparent magnitudes
    • xX,xY,xZ,xVX,xVY,xVZ : error-free cartesian galactocentric coordinates (kpc) and velocities (km/s)
    • xl_deg,xb_deg,xRhel_kpc,xmulcosb_masyr,xmub_masyr,xvrad : error-free observables (l,b, heliocentric distance in kpc, proper motions in mas/yr, radial velocities in km/s)
    • gX,gY,gZ,gVX,gVY,gVZ : error-convolved cartesian galactocentric coordinates and velocities.
    • gl_deg,gb_deg,gRhel_kpc,gmulcosb_masyr,gmub_masyr,xvrad : error-convolved observables
    • IDstream: progenitor ID. Stars with same IDstream come were accreted in the same progenitor.
• LJMU001.progenitor.tracer.info
• LJMU006.progenitor.tracer.info
  • Progenitor info file structure:
    • IDstream, TreeID: progenitor ID, TreeID (alternative progenitor ID)
    • infallZ,mlogage_yr,mZmetal : progenitor's infall redshift, mean log(age) and mean metallicity of stellar population
    • NKIII_all, NKIII_G20 : total number and Gaia observable (G<20) number of K giants stars in progenitor

These are provisional files provided for Gaia Challenge purposes (potential fitting and stream finding challenges). The final set for all haloes will be published in Mateu et al. in prep.

When making use of data in this part of the challenge, please cite the Gaia Challenge Wiki and Mateu et al. in prep. For any questions please contact: Cecilia Mateu (cmateu@astrosen.unam.mx) or Andreea Font (A.S.Font@ljmu.ac.uk)

How many tidal stellar streams will be detected by Gaia? Use a series of N-body simulations of Milky Way-type galaxies to predict the number and properties of streams to be detected by Gaia in the stellar halo.

(Last update: 11/May/2015)

Try to recover the progentior DM distribution (cusp/core) from clean and noisy mock data of stellar streams!

See arXiv:1501.4968 section 2 for detailed parameters. Host: axis-symmetric potential (spherical NFW + Hernquist bulge + Miyamoto-Nagai disk). Dwarf galaxy: Dehnen models on eccentric planar orbit. The simulations were run with 2e7 particles using the PM code Superbox, with inner grid resolution of 2kpc/128 and time step 1Myr. Format of data files: x,y,z, vx,vy,vz, p where p is the probability for a DM particle to tag a star. Positions in kpc, velocities in km/s. (0,0,0) is the galactic centre. Each file contains data for 1e6 randomly chosen particles.

Noisy mock data: errors are gaussian, centred on the correct value, with sigma of 1km/s for velocities and R/10 for positions, where R is the distance to the sun fixed at (x,y,z) = (-8kpc,0,0).

Get the data files here: www.roe.ac.uk/~raer/gaia2015. If you have any questions or input, send me a mail to raer[at]roe.ac.uk .