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Reconciling Dwarf Galaxies with LCDM Cosmology Andrew Wetzel Moore Prize Fellow Carnegie Fellow in Theoretical Astrophysics with the F RE collaboration Feedback In Realistic Environments dwarf galaxies present the most significant challenges to the Cold Dark Matter (CDM) model Andrew Wetzel Caltech - Carnegie Context: Milky Way satellites and “crises” of ΛCDM satellite dwarf galaxies: simulated vs observed >105 identified subhalos 12 bright satellites (LV > 105 L ) V. Springel / Virgo Consortium J. Bullock Andrew Wetzel Caltech - Carnegie Kravtsov et al 2010 100 N(> Vcirc ) dark-matter subhalos in dark-matter-only simulations 10 observed dwarf galaxies around the Milky Way 1 10 20 30 40 Vcirc (km/s) 50 60 70 Vmax ⇡ r GMtotal r “missing satellites” problem: too few observed satellites ΛCDM satellites compared with dark-matter subhalos in CDM Local group dwarfs Andrew Wetzel Caltech - Carnegie and Mateo, Olszewski & Walker 2 is analytically exact for sphericall velocity dispersion profiles. Howe systems the mass (circular velocity by as much as 40 per cent (18 per cen the long-axis, and similarly overesti (22 per cent) if viewed from along t 2013). Shifts of order 20 per cent in of the error bars on Draco and Ursa M r our overall conclusions. Other mass GM2013; r)& G tot (< Breddels & Helmi Jardel Vcirc (r) = are consistent with those r plotted in The points in Fig. 3 are sized by th galaxy. Plotted in black are the lowmagenta points indicate the high-d Minor, which may only be associate host (indicated by the dotted magen failures. If the data points for Draco Boylan-Kolchin 2012 higher (e.g. if Vet were underestima 1/2al Garrison-Kimmel et vanish al 2014 (cyan lines) would but the nu and black lines) would remain unch Fig. 4 summarizes the results of complete set of 48 hosts, where eac “too3. big fail” problem: dark-matter in CDM assumed density profile are shape. Bl Figure Rotationto curves, assuming Einasto profiles with α = 0.18, of subhalos −1 within 300 kpc of the centre fiducial choice, an α = 0.18 Eina all resolved haloes with V > 30 km s peak too dense compared with observed satellite galaxies of Douglas (based on measured Vmax and Rmax values in the simulation). implied distributions for NFW pro Plotted as Wetzel black points are the data for the MW satellites brighter than Caltech Carnegie Einasto (cyan; α =-0.28), and an o Andrew dwarf galaxies: the most significant challenges to the Cold Dark Matter (CDM) model “missing satellites” problem (probably) too few observed satellite galaxies compared with dark-matter subhalos in CDM —> Can a CDM-based model produce a satellite stellar mass function as observed? “too big to fail” problem dark-matter subhalos in CDM are too dense compared with observed satellite galaxies —> Can a CDM-based model produce a satellite dynamical mass (velocity dispersion) function as observed? Andrew Wetzel Caltech - Carnegie The Local Group Weisz et al 2014 Andrew Wetzel Caltech - Carnegie distance to MW or M31 [kpc] Wetzel et al 2015 MW halo radius ~300 kpc limited observational completeness of dwarf galaxies Andrew Wetzel Caltech - Carnegie cosmological hydrodynamic simulations of Milky Way-mass galaxy to z = 0 0.1 Latte (better —>) 1 10 FIRE 100 1000 resolve dwarf galaxies GARROTXA Agertz&Kravtsov Sawala Eris CLUES Mollitor Massive MAGICC GASOLINE Eagle Black-II Illustris Aquarius (AREPO) NIHAO (better —>) Andrew Wetzel Caltech - Carnegie The Latte Project: the Milky Way on FIRE Simulating a Milky Way-mass galaxy with a realistic population of satellite dwarf galaxies at parsec resolution Wetzel et al 2016, ApJL submitted, arXiv:1602:05957 F RE Feedback In Realistic Environments F RE model for star formation Feedback In Realistic Environments http://www.astrophoto.com/M82.htm Ultra-high resolution mgas = 7000 Msun hgas = 1 pc (hdm = 20 pc) captures multi-phase inter-stellar medium Cooling from atoms, molecules, and 9 metals down to 10 K Star formation only in self-gravitating clouds: nH >~100 cm-3 Star formation efficiency: 100% per free-fall time Andrew Wetzel ESA Caltech - Carnegie F RE model for stellar feedback Feedback In Realistic Environments Heating: Supernovae: core-collapse (II) and Ia http://www.astrophoto.com/M82.htm Stellar Winds: massive O-stars & AGB stars 30 Doradus Photoionization (HII regions) Explicit Momentum Flux: Radiation Pressure Ṗrad L ⇠ (1 + c IR ) Supernovae 1 ṖSNe ⇠ ĖSNe vejecta Stellar Winds ṖW ⇠ Ṁ vwind Andrew Wetzel ESA Caltech - Carnegie . n n t f r h s a Galaxy Stellar Mass [Mstar/fbMhalo] a s e n t e e f l no feedback FIRE feedback Hopkins et al 2014 log Halo Mass [Msun]Figure 4. Galaxylog Halo Mass [Msun] stellar mass-halo mass relation at z = 0. Top: M (M ∗ halo ). Figure 6. M⇤ Mhalo relation at z = 0, as Fig. 4. Top: Simulations with Bottom: M relative to the Universal baryon budget of the halo (fb Mhalo ). different numerical parameters: we show the effects of varied resolution, ∗ Each simulation (points) from Table 1 is shown; large point denotes the most artificial viscosity, and the algorithmic implementation of feedback. We massive halo in each box. We compare the relation if all baryons became also compare a completely different version of SPH (with a different set stars (M∗ = fb Mhalo ; dotted) and the observationally inferred relationship of hydrodynamic equations), which is known to differ significantly as in determined cerin Moster, Naab & White (2013, magenta) and Behroozi, tain idealized hydrodynamic test problems. These have little effect Wechsler on our & Conroy (2013, cyan) – dashed lines denote extrapolation beyond predictions. Bottom: Effect of physical variation in stellar feedbackthepropobserved range; see footnote 9. The agreement with observations is erties. We compare runs with no stellar feedback, with no supernovae (but at Mhalo ! 1013 M , including dwarf though MW-mass galaxies. excellent relation between galaxy stellar mass and host halo virial mass emerges naturally Andrew Wetzel ⊙ Caltech - Carnegie log SFR density [Msun/yr/pc2] ⌃˙ ⇤ ⇠ ⌃gas /⌧dyn Galaxies on FIRE: ⌃˙ feedback ⇠ 0.02and⌃star formation /⌧ ⇤ gas dyn 591 Hopkins et al 2014 d e erv s ob log gas density [Msun/yr/pc2] 2 log gas density [M sun/yr/pc ] Figure 8. KS-law, observed (Kennicutt 1998; Bigiel et al. 2008; Genzel et al. 2010; Daddi et al. 2010, yellow shaded range) and simulated (points as Fig. 4). We emphasize that this is a prediction: the instantaneous star formation efficiency per dynamical time in dense gas is 100 per cent in the simulations, but the emergent KS-law, as a consequence of feedback, has an efficiency a factor ∼50 lower. As shown in Paper I and Hopkins et al. (2013c), this is insensitive, with resolved feedback models, to the smallscale star formation law, and entirely determined by stellar feedback. ‘No feedback’ models lie a factor ∼50 above the observations; ‘no radiation’ and ‘no SNe’ models (Fig. 6) lie a factor ∼10 above observations. Kennicutt-Schmidt relation emerges naturally Andrew Wetzel Caltech - Carnegie Latte: cosmological zoom-in simulation dark matter M200m=1.3x1012 Msun 6 Mpc Latte: cosmological zoom-in simulation stars 6 Mpc dark matter only simulation 600 kpc dark matter with effects of baryons 600 kpc stars 600 kpc Mstar = 9x1010 Msun SFR = 3.4 Msun/yr 20 The Latte Project: the Milky Way on FIRE Population of satellite dwarf galaxies F RE Feedback In Realistic Environments Andrew Wetzel Caltech - Carnegie stellar mass function of satellites Wetzel et al 2016 Andrew Wetzel Caltech - Carnegie stellar mass function of satellites Wetzel et al 2016 Andrew Wetzel Caltech - Carnegie stellar velocity dispersion function of satellites Wetzel et al 2016 Andrew Wetzel Caltech - Carnegie stellar velocity dispersion function of satellites Wetzel et al 2016 Andrew Wetzel Caltech - Carnegie velocity dispersion - mass relation Wetzel et al 2016 Andrew Wetzel Caltech - Carnegie velocity dispersion - mass relation Wetzel et al 2016 Andrew Wetzel Caltech - Carnegie mass - metallicity relation Kirby et al 2014 Wetzel et al 2016 Andrew Wetzel Caltech - Carnegie mass - metallicity relation Wetzel et al 2016 Andrew Wetzel Caltech - Carnegie diverse range of star-formation histories of satellite dwarf galaxies Weisz et al 2014 Andrew Wetzel Caltech - Carnegie diverse range of star-formation histories of satellite dwarf galaxies Wetzel et al 2016 Andrew Wetzel Caltech - Carnegie What causes the lack of (massive) satellite dwarf galaxies around the Milky Way-mass host? 1. Stellar feedback forms dark-matter cores by driving significant gas outflows/inflows that transfer orbital energy to dark matter 2. Stellar disk of the Milky Way-mass host galaxy destroys satellites (via tidal shocking, etc) Andrew Wetzel Caltech - Carnegie inclusion of baryons destroys dark-matter subhalos dark matter in dark-matter-only dark matter in baryonic simulation Andrew Wetzel Caltech - Carnegie subhalo number density profile su bh alo si n da rk -m at subhalos in baryonic te ro nly Mbound >1e7 Msun Wetzel et al in prep Andrew Wetzel Caltech - Carnegie dark-matter halo mass function ha lo ha los in s in da rk ba ry -m on ic at te ro nl y d >1000 kpc Wetzel et al in prep Andrew Wetzel Caltech - Carnegie dark-matter subhalo mass function su bh a lo s in da rk - m su bh alo at s in te r on ly ba ryo nic d < 300 kpc Wetzel et al in prep Andrew Wetzel Caltech - Carnegie x A Modest Proposal “LCDM predicts…” (dark energy + cold dark matter) “LCDMB predicts…” (dark energy + cold dark matter + baryons) Andrew Wetzel Caltech - Carnegie The Latte Project: the Milky Way on FIRE F RE Feedback In Realistic Environments http://www.astrophoto.com/M82.htm stellar mass function velocity dispersion function mass - metallicity starformation histories Andrew Wetzel Caltech - Carnegie