Observed MW satellites Testing Cosmology with Phase-Space Correlations in Systems of Satellite Galaxies Current Studies and Future Prospects http://marcelpawlowski.com/research/movies-astronomy/ Marcel S. Pawlowski Hubble Fellow at University of California Irvine (2006) et al. Diemand Email: [email protected] Twitter: @8minutesold Web: marcelpawlowski.com Simulated DM subhalos Is the phase-space distribution of satellite galaxies consistent with ΛCDM expectations? • 40-50 known satellite galaxies for both Milky Way and Andromeda. • Numerous small-scale problems known (missing satellites, core-cusp, TBTF) but affected by baryonic physics • Positions and velocities of satellite sub- halos on ≥100 kpc scales robust against internal baryonic physics and feedback processes. • Radial distribution is affected. Ahmed+2017, Garrison-Kimmel+2017 Via Lactea project / J. Diemand Lactea project Via Phase-space correlations • Close pairs of galaxies • Groups of galaxies / group infall • Planes of satellite/dwarf galaxies • Lopsided satellite systems Phase-space correlations • Close pairs of galaxies • Groups of galaxies / group infall • Planes of satellite/dwarf galaxies • Lopsided satellite systems Pairs of Satellites (of similar magnitude) Fattahi et al. (2013) Observed LG: ΛCDM simulations: 28% in close pairs 6% in close pairs with similar velocity with similar velocity Phase-space correlations • Close pairs of galaxies • Groups of galaxies / group infall • Planes of satellite/dwarf galaxies • Lopsided satellite systems Crater-Leo group of MW satellites Pawlowski, McGaugh & Sohn (in prep.) • 4 satellite galaxies + 1 star cluster (Crater 1). • Suggested by e.g. Torrealba et al. (2016) to be one infalling group. 1.Aligned along one common great circle. 2.Coherent distance trend along this direction (symbol sizes). 3.Similar, low Galactocentric velocities. 4.Typical number for ‘normal’ ΛCDM sub- halo groups found in simulations (2-5, VPOS e.g. Li & Helmi 2009). 5.Leo II and Leo IV stopped star formation ~5 Gyr ago: common infall at that time? 6.Leo II proper motion (Piatek et al. 2016) consistent with orbit along this direction (but VPOS too). Phase-space correlations • Close pairs of galaxies • Groups of galaxies / group infall • Planes of satellite/dwarf galaxies • Lopsided satellite systems The Vast Polar Structure of the Milky Way (VPOS) Pawlowski, Pflamm-Altenburg & Kroupa (2012, MNRAS, 423, 1109), Pawlowski & Kroupa (2013, MNRAS, 435, 2116), Pawlowski, McGaugh & Jerjen (2015, MNRAS, 453, 1047) Majority of MW satellites with measured proper motions co-orbit along VPOS CVn II CVn Com Leo II Crater-Leo group Willman 1 Boo UMa I Segue 1 or part of the Boo III VPOS? Boo II UMi Leo V Leo I Leo IV Draco Her Crater UMa II Hya II Sextans Segue 3 Sgr Tri II Kim 1 Car Kim 2 LMC SegueBoth 2 MW satellite pairs SMC Peg III Tuc II have similar PMs Pic I Ret II Pisces II Gru I Hor II Phe II Hor I Eri III For Scl The VPOS as seen from outside the Milky Way Pawlowski 2018 (brief review in MPLA, arXiv:1802.02579) How does the VPOS compare to ΛCDM? Pawlowski 2018 (brief review in MPLA, arXiv:1802.02579) (11 classical satellites only!) Observed VPOS Frequency of similarly extreme satellite arrangements in cosmological simulations is ≤ 0.1% Measure of kinematic coherence Measure Measure of plane width Is the Milky Way special? The Great Plane of Andromeda (GPoA) Ibata+2013 Both M31 satellite pairs are part of the GPoA Measure of kinematic coherence Measure Measure of plane width Frequency of similarly extreme satellite arrangements in cosmological simulations is ≤ 1%, ≤0.1% if considering radial distribution. Is the LG special? Cen A Satellite Plane Müller, Pawlowski, Jerjen & Lelli (2018) Measure of kinematic coherence Measure Measure of plane width Frequency of similarly extreme satellite arrangements in cosmological simulations is ≤ 0.5% (DMO & hydro simulations) Searching for a Satellite Planes Signal in a Statistical Sample of Systems Ibata et al. 2014 • Identify hosts with ≥2 satellites with measured los velocities in SDSS. • Select satellites on opposite sides -> increases chance to see satellite plane edge-on. • Check velocity relative to host: • ΛCDM expectation: 50% have correlated, 50% have anti-correlated velocity sign. • Rotating satellite planes: satellite pairs should show anti-correlated velocities. • Observed velocity anti-correlation consistent with > 60% of satellites in thin planes. (Ibata et al. 2014) Phase-space correlations • Close pairs of galaxies • Groups of galaxies / group infall • Planes of satellite/dwarf galaxies • Lopsided satellite systems Libeskind et al. (2016): Lopsidedness in stacked host pairs in SDSS θ 20 7 . θ Lopsidedness of Satellite Systems in Simulations Pawlowski, Ibata & Bullock (2017) • Cumulative number of satellites Observed vs. Simulated 1.15 MS1 (no orphans) facing partner in wedges of opening angle θ. MS1 (no orphans) opposite partner MS2 (no orphans) facing partner • Observed overabundance MS2 (no orphans) opposite partner SDSS facing partner 1.10 (black). Libeskind+2016 SDSS opposite partner • Millennium 1+2 simulations show such an excess! Pawlowski+2017 1.05 • ΛCDM passes this test. 1.00 θ 0.95 ratio of found vs. expected from isotropy 0.90 0 10 20 30 40 50 60 70 80 90 cos (✓) ≥| | Limitations of Studying Phase-Space Correlations in Satellite Galaxy System Target Milky Way Andromeda Centaurus A Local Volume (~ 100 Mpc) (distance) (~100 kpc) (~800 kpc) (~4 Mpc) (~10 Mpc) Angular size of viral volume all-sky 18º 4º 1.4º 9’ (rvir~ 250 kpc) 5% distance ± 5 kpc ± 40 kpc ± 200 kpc ~ 500 kpc ~ 5 Mpc uncertainty Positions 3D 3D ~3D 2D 2D 3D 1D - 3D 1D 1D 1D Kinematics LoS + PM LoS (+ PM?) LoS LoS LoS Angular size of dwarf 9’ 1’ 0.2’ 5” 0.5” (rh ~ 250 pc) Limitations of Studying Phase-Space Correlations in Satellite Galaxy System • Less phase-space information available for distant satellite systems. ➡ Must test correlations in projection. ➡ Need to study more host systems. • Need better statistics to investigate connections between different types of phase-space correlations. • Is is universal or incidental? • Velocity information is crucial (2D -> 3D). • Not only for top 1-2 satellites, but for ≥ 10, i.e. down to MV ~ -8 Some Current Surveys Spectroscopic Satellite Survey Around NGC 4258 (Spencer, Loebman & Yoachim, 2014) • d=7.6 Mpc, luminosity limit for satellite velocities: MV < −11 (Sculptor) 1.5 450 SAGA Probablesurvey Satellites (Geha et al. 2017) 600 Possible Satellites 350 Probable Satellites • 1.0Aim: dwarf satellite galaxy systems down to Mr Possible Satellites 634 400 634 080 250 207 < −12.3 (Leo I) in 300 kpc viral radius around 593 521 621 0.5 593 100 MW analogs between521 20-40150 Mpc.200 190 080 ) 207 1 190 − 480 072 092 090 ) 0.0 (km/s) 072 ° 50 (kms 436 0 Limits correspond996 to top 5-6 MW sats. (LMC, 277 277 NGC 4258 NGC4258 Dec ( −0.5 −50 V V −200 SMC, Sag, For, Leo I, Scu) − 860 996 860 −150 V ➡ Not enough to study480 phase-space structures −1.0 092 −400 −250 621 −1.5 436 −600 −350 0 50 100 150 200 250 090 RProj (kpc) −2.0 −450 1.5 1.0 0.5 0.0 −0.5 −1.0 −1.5 −2.0 RA (°) Conclusions 1. The phase-space distribution of satellite galaxies is a powerful test of cosmological models: • Does not depend strongly on baryonic physics. • LCDM predicts correlations which haven’t been observationally confirmed (e.g. groups of satellites). 2. Satellite phase-space distributions show a number of conflicts with ΛCDM expectations: Planes of Satellite galaxies, too many satellite pairs, … 3. Most severe tension with LCDM due to kinematics, not distribution alone. ➡Need line-of-sight velocities! 4. Have to study a statistical sample of satellite systems. For more on satellite planes, see my review in MPLA: arXiv:1802.02579.