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-====== Streams & Halo Stars ======
-Go to internal page: http://astrowiki.ph.surrey.ac.uk/dokuwiki/doku.php?id=streamgroup_internal
-These mock data are designed to mimic cold/hot streams in the Milky Way halo and the halo star population. Key questions are:
-(1) What can we learn about the gravitational potential from such cold streams or halo stars? (2) Can we find clear evidence for triaxiality? (3) Can we find any evidence for granularity or substructure in the potential?
-If posting new tests, please try to approximately follow the template set out for the "spherical collisionless tests" [[:sphtri|here]].
-**Key working group coordinator:** Andreea Font
-===== Spherical Halo =====
-Robyn Sanderson has created a mock Galactic stellar halo for use in testing various algorithms for recovering the Milky Way's gravitational potential from measurements of the phase space positions of tidal streams. Currently the test data for a spherical halo is available and axisymmetric and triaxial potentials will be added shortly. The process generating the satellites that dissolve into streams is decoupled from the potential in which the streams are integrated, so that the same set of progenitor satellites can be compared across different potentials.
-This challenge comes in two parts: (I) determine the form of the spherical potential in which the streams are orbiting and (II) determine the best-fit parameters for that form. You may choose to do part II only, or both parts I and II.
-The mock halo has been provided by Robyn Sanderson (questions/comments to sanderson at astro dot rug dot nl) and can be downloaded as a tarball from [[http://www.astro.rug.nl/~sanderson/GaiaStreamChallenge_Spherical.tgz|here]]. The files in the tarball are as follows:
-**InitialConditions.pdf** gives the details of how the halo was generated. This document deliberately doesn't contain the true parameters of the potential or its form, so you may read freely without fear of spoilers.
-If you wish to try recovering just the parameters and not the form of the potential (part II), the form of the potential used for the halo is found in **potentialForm.pdf**. If you want to also recover the form (part I), use this file to check your work. The potential parameters are revealed in the document **potentialParameters.pdf**.
-The tarball includes 5 ASCII data files that are listed below. In all files, the first line is the number of lines after that line in the file. So to read things in, read the first integer to get n_lines, then read n_lines of data.
-**MilkyWay1.dat** includes the positions (in kpc) and velocities (in km/s) of the stars in the halo after convolution with the Gaia error model.
-**MilkyWay1.ne.dat** are the same positions/velocities before error convolution.
-**MilkyWay1.obs.dat** are the coordinates and errors in the observed space. The 11 columns are visual magnitude, right ascension (rad), declination (rad), parallax (mas), par error, mu_alpha (proper motion in RA, mas/yr), pm error, mu_delta (proper motion in dec, mas/yr), pm error, radial velocity (km/s), RV error.
-**MilkyWay1.sats.dat** is a list of the locations of the first star in each progenitor satellite in the above three files. The stars are in the same order in all three files, sorted by progenitor, so the stars belonging to progenitor i are at positions sats(i):(sats(i+1) -1) in the arrays holding the positions/velocities (assuming zero-indexed arrays).
-**MilkyWay1.info.dat** contains the properties of the progenitor satellites that produced the streams in the data set. The 9 columns are satellite ID# (from the larger sample that these are drawn from), total number of [RGB] stars in the satellite, 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 [from 0 (=radial) to 1 (=circular)].
-A copy of this page is also included as **README.html**.
-====Publication policy====
-When making use of this data, please cite the Gaia Challenge Wiki and Sanderson, Helmi, & Hogg 2014, in Proc. IAU Symposium 298, Setting the Scene for Gaia and LAMOST, ed. S. Feltzing, G. Zhao, N.A. Walton & P.A. Whitelock. A short description of the creation of the mock stellar halo is in section 2 of this report. Stay tuned: this reference should change soon as a more complete description is submitted in the next few months.
-Good luck!
-=====Stellar Substructure in the Galactic Halo=====
-Ana Bonaca, Adrian Price-Whelan and Andreas Küpper have designed a challenge to model stellar streams in the Galactic halo. The challenge comes in three complementary parts: (1) a warm dwarf galaxy stream and (2) a cold globular cluster stream, both computed in a static, analytic Milky Way-like potential, and (3) a set of cold streams created in a live dark matter potential.
-====1. The Sagittarius Stream====
-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. [[http://astrowiki.ph.surrey.ac.uk/dokuwiki/lib/exe/fetch.php?media=sgr.zip | Download the challenge here]]. Contact Adrian for questions: <adrn@astro.columbia.edu>
-===Specifications===
-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.
-===Part 1===
-//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 [[http://www.google.com/url?q=http%3A%2F%2Fwww.rssd.esa.int%2Findex.php%3Fpage%3DScience_Performance%26project%3DGAIA&sa=D&sntz=1&usg=AFQjCNHf04vX6b57rA3USDdeS32hx6h8ew | Gaia proper-motion errors]], photometric distance errors (~15%), and 20 km/s radial velocity errors, typical for RR Lyrae.
-===Part 2===
-//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 [[http://www.google.com/url?q=http%3A%2F%2Fwww.rssd.esa.int%2Findex.php%3Fpage%3DScience_Performance%26project%3DGAIA&sa=D&sntz=1&usg=AFQjCNHf04vX6b57rA3USDdeS32hx6h8ew | Gaia proper-motion errors]], mid-IR PL distance errors (2%), and 20 km/s radial velocity errors typical for RR Lyrae.
-===Misc.===
-//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.
-===Publication policy===
-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.
-====2. The Palomar 5 Stream====
-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 [[http://www.ast.cam.ac.uk/~sverre/ | NBODY6]] (see Aarseth, 2003, Gravitational N-Body Simulations, Cambridge University Press). [[http://astrowiki.ph.surrey.ac.uk/dokuwiki/lib/exe/fetch.php?media=pal5.tar.gz | Download the challenge here]]. Contact Andreas for questions: <andreas.kupper@yale.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 [[http://astrowiki.ph.surrey.ac.uk/dokuwiki/lib/exe/fetch.php?media=pal5_gaia.tar.gz | 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.
-===Specifications===
-The file //pal5.all_particles.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.
-{{ :pal5.all_particles_w_errors.png?400 |}}
-{{ :pal5.all_particles_w_errors_vr.png?200 |}}
-===Publication policy===
-When making use of data in this part of the challenge, please cite the Gaia Challenge Wiki; and Küpper et al., in prep.
-====3. The Via Lactea Streams====
-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. [[http://astrowiki.ph.surrey.ac.uk/dokuwiki/lib/exe/fetch.php?media=vl2.tar.gz | Download the challenge here]]. Contact Ana for questions: <ana.bonaca@yale.edu>
-This part of the challenge comes in two parts:
-. What is the best-fit potential of the VL2 at z=0 given a certain stream?
-. 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?
-===Specifications===
-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.
-===Publication policy===
-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., in prep.
-=====Aquarius Challenge=====
-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.
-===Stream catalogue===
-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 stars that were once a member of the progenitor satellite. In each case while the majority of stars 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 stars in the file. The following data files are available:
-[[http://astro.dur.ac.uk/~bjl/gaia/AquariusA2streams.ne.dat | AquariusA2streams.ne.dat]] - Positions and velocities of stars 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.
-[[http://astro.dur.ac.uk/~bjl/gaia/AquariusA2streams.dat | 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 of stars (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.
-===Complete mock catalogue===
-A complete mock catalogue containing all the stars in the accreted stellar halo is also available at http://galaxy-catalogue.dur.ac.uk:8080/Millennium, as a public SQL database, StellarHalo, (in beta) of 100,000,000 stars (with M_g<7). Streams can be found within the catalogue by searching for all stars with the same subhaloBranchID and checking whether they form a coherent structure.
-Additional information is available about the halo, including the dark matter particle data and subhalo catalogues. Contact Ben Lowing for questions <b.j.lowing@durham.ac.uk>
-==Publication policy==
-When making use of data in this part of the challenge, please cite the Gaia Challenge Wiki; and Lowing et al., in prep.
-=====Ensemble of streams in NFW Halo + Hernquist Bulge + Miyamoto & Nagai Disk=====
-(Raphael, erraph[at]gmail[dot]com)
-I'm running N-Body simulations in a static potential consisting of a spherical NFW Halo (ApJ, 490, 493), a spherical Hernquist Bulge (ApJ, 356, 359) and an axis-symmetric Miyamoto & Nagai Disk (PASJ, 27, 533
-).
-{{http://dl.dropboxusercontent.com/u/9718909/Gaia/1.png?450}}{{http://dl.dropboxusercontent.com/u/9718909/Gaia/2.png?200}}
-You get full phase space information in a galactocentric cartesian frame of reference.
-I'll post ASCII files for 10^6 mass points each here soon, containing both stream and progenitor.
-There is self-interaction between the stream particles and between progenitor and stream.
-The progenitor has a Dehnen (MNRAS, 265, 250) density profile, if you prefer I can provide a selection of central stars following a Plummer profile.
-Here's the first stream. It's more a stream of CDM then of stars, because I uploaded phase space data for all mass points, but I can paint the mass points with a probability of being a star drawn from a Plummer profile. The total mass is 10^9 solar masses, the dwarf had 8 Gyrs of time to be stripped.
-Just let me know if the format is o.k. for you, then I'll upload more streams with different orbits, and if you want also with different masses / numbers of stars.
-{{http://dl.dropboxusercontent.com/u/9718909/Gaia/1stStream.png?450}}
-The file format is x,y,z,vx,vy,vz in kpc and km/s, galactocentric reference frame. If you need I can also add Lambda and B for a galactocentric reference frame.
-For simplicity I provide distinct files for the progenitor and the stream.
-[[https://dl.dropboxusercontent.com/u/9718909/Gaia/stream_1.tar.gz]]
-=====12 different streams in the same spherical potential=====
-(Hans Buist, buist[at]astro[dot]rug[dot]nl)
-I have prepared several simulations of testparticle streams in a fixed spherical NFW potential. I have run the code for 12 different orbits. The particles have been evolved for roughly 8 Gyr. Can you find the scale mass and radius of the potential?
-(I also have time-evolving potentials available if anyone wants to try those. )
-These files are provided as ASCII files with rows of 6 coordinates, with the first particle being the location of the 'progenitor', the others being the stream.
-{{https://www.dropbox.com/sh/attgn8qu6g1k67g/o8th14bQaj}}
-======Evolving streams======
-(Hans Buist, buist[at]astro[dot]rug[dot]nl)
-Here I provided 2 different streams evolved in a spherical NFW potential, evolving in time. Data again in ASCII files.
-==== Description of Potential ====
-{{:description1.png?400|Description of Potential}}
-Note: currently only Sculptor
-==== Description of Simulation ====
-{{:description2.png|Description of Simulation}}
-==== Used Cosmology ====
-  * Omega_m = 0.29
-  * Omega_m + Omega_Lambda = 1.0
-  * h_100 = 0.71
-==== Files ====
-Positions are in kpc, velocities in kpc/Gyr (~km/s). The first particle is the position of the 'progentor' today.
-  * {{http://www.astro.rug.nl/~buist/GAIAChallengeorb1.ac8.50000.300.101.txt}} ("Sculptor", Orbit 1)
-  * {{http://www.astro.rug.nl/~buist/GAIAChallengeorb2.ac8.50000.300.101.txt}} ("Sculptor", Orbit 2)
-  * {{http://www.astro.rug.nl/~buist/GAIAChallengeorb1.ac0.50000.300.101.txt}} ("Sculptor", Orbit 1, fixed potential)
-  * {{http://www.astro.rug.nl/~buist/GAIAChallengeorb2.ac0.50000.300.101.txt}} ("Sculptor", Orbit 2, fixed potential)
-==== Publication policy ====
-Soon this evolution model for potentials will be published in a research note :-). If you use them, please reference Buist & Helmi 2013 (in prep)