The importance of tides for the Local Group dwarf spheroidals

By Justin I. Read, M. Wilkinson, N. Evans II, G. Gilmore, J. Kleyna. 2005

143 citations recorded by the source corpus.

There are two main tidal effects that can act on the Local Group dwarf spheroidals (dSphs): tidal stripping and tidal shocking. Using N-body simulations, we show that tidal stripping always leads to flat or rising projected velocity dispersions beyond a critical radius; it is ∼5 times more likely, when averaging over all possible projection angles, that the cylindrically averaged projected dispersion will rise, rather than be flat. In contrast, the Local Group dSphs, as a class, show flat or falling projected velocity dispersions interior to ∼1 kpc. This argues for tidal stripping being unimportant interior to ∼1 kpc for most of the Local Group dSphs observed so far. We show that tidal shocking may still be important, however, even when tidal stripping is not. This could explain the observed correlation for the Local Group dSphs between central surface brightness and distance from the nearest large galaxy. These results have important implications for the formation of the dSphs and for cosmology. As a result of the existence of cold stars at large radii in several dSphs, a tidal origin for the formation of these Local Group dSphs (in which they contain no dark matter) is strongly disfavoured. In the cosmological context, a naive solution to the missing satellites problem is to allow only the most massive substructure dark matter haloes around the Milky Way to form stars. It is possible for dSphs to reside within these haloes (∼10 10 M� ) and have their velocity dispersions lowered through the action of tidal shocks, but only if they have a central density core in their dark matter, rather than a cusp. A central density cusp persists even after unrealistically extreme tidal shocking and leads to central velocity dispersions which are too high to be consistent with data from the Local Group dSphs. dSphs can reside within cuspy dark matter haloes if their haloes are less massive (∼10 9 M� ) and therefore have smaller

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

RECONCILING DWARF GALAXIES WITH ΛCDM COSMOLOGY: SIMULATING A REALISTIC POPULATION OF SATELLITES AROUND A MILKY WAY–MASS GALAXY (2016, background): “More concretely, the “too big to fail” problem: dark-matter-only simulations predict too many massive dense subhalos compared with satellites around the MW (Read et al. 2006; Boylan-Kolchin et al. 2011).”
The stellar mass-halo mass relation of isolated field dwarfs : a critical test of ΛCDM at the edge of galaxy formation (2016, background): “Cored dwarfs are much more susceptible to tidal shocking and stripping on infall to a larger host galaxy (e.g. Read et al. 2006; Peñarrubia et al. 2010; Brooks et al. 2013).”
Cusp-core transformations in dwarf galaxies: observational predictions (2012, methodology): “Initial positions and velocities were computed using the density–potential pair approach of Kazantzidis, Magorrian & Moore (2004), later refined by Read et al. (2006a).”
THE SAGITTARIUS DWARF GALAXY: A MODEL FOR EVOLUTION IN A TRIAXIAL MILKY WAY HALO (2010, background): “…nature of the stripping, and the dependence of the effectiveness of tidal stripping on the orientation of individual stellar orbits (see, e.g., Read et al. 2006a) means that on any given pericentric passage Galactic tides reach deeply into the satellite and can unbind stars from a variety of…”
Thin, thick and dark discs in ΛCDM (2008, methodology): “Toomre & Toomre (1972) attribute the phenomenon to increased resonance in the prograde case, but one can also think of it in terms of increased tidal forces for the prograde interaction (see e.g. Read et al. 2006b).”
The Velocity Dispersion Profile of the Remote Dwarf Spheroidal Galaxy Leo I: A Tidal Hit and Run? (2007, methodology): “Models of dSph galaxies that lack DM but are optimally aligned to conceal structural anomalies still tend to exhibit larger centroid shifts and isophote variations thanwe observe in Leo I (Klessen& Kroupa 1998; Klessen & Zhao 2002; Fleck & Kuhn 2003; Read et al. 2006b).”
Dark matter cores and cusps: the case of multiple stellar populations in dwarf spheroidals (2011, background): “The metal-poor population may have undergone thermalization with the help of impulsive tidal stirring near the pericenters of orbits and of dynamical instabilities driven by the tidal field near the apocenters (e.g., Read et al. 2006; Klimentowski et al. 2007).”
The local dark matter density (2014, background): “7Apart from especially resonant situations, the above formula that owes to Chandrasekhar (1943) works remarkably well (Read et al., 2006a).”
Not so lumpy after all: modelling the depletion of dark matter subhaloes by Milky Way-like galaxies (2017, background): “As Brooks & Zolotov (2014) showed, the increased tidal forces from the central galaxy also can reduce the central masses of such dwarf galaxies even further, potentially eliminating the disagreement between theory and observations entirely (also see Read et al. 2006a,b).”
Forged in FIRE: cusps, cores and baryons in low-mass dwarf galaxies (2015, background): “We have not considered the effects stripping from ram pressure and tides, that may be important for some Milky Way subhalos (Read et al. 2006; Zolotov et al. 2012; Brooks & Zolotov 2014).”
Dark matter cores all the way down (2015, methodology): “This can be avoided if there is a central constant density core that causes dynamical friction to stall (Goerdt et al. 2006; Read et al. 2006a).”
Ultralight scalars as cosmological dark matter (2016, background): “These studies [107, 108] indicate that the expected number of luminous secondary galaxies is absent, and much work is being done to see if feedback from massive stars and black-hole outflows, or other baryonic physics, can account for the deficit.”
WHY BARYONS MATTER: THE KINEMATICS OF DWARF SPHEROIDAL SATELLITES (2012, background): “…stripping after infall to reduce the DM masses of satellite galaxies (Gnedin et al. 1999; Taylor & Babul 2001; Hayashi et al. 2003; Kazantzidis et al. 2004; Kravtsov et al. 2004; Read et al. 2006; Sales et al. 2007b; Muñoz et al. 2008; D’Onghia et al. 2010; Choi et al. 2009; Collins et al. 2011).”
BARYONS MATTER: WHY LUMINOUS SATELLITE GALAXIES HAVE REDUCED CENTRAL MASSES (2012, background): “The tidal effects of a disk are expected to be increasingly stronger as the central density profile of satellites becomes shallower (Taylor & Babul 2001; Stoehr et al. 2002; Hayashi et al. 2003; Read et al. 2006a; Peñarrubia et al. 2010).”
SUBSTRUCTURE DEPLETION IN THE MILKY WAY HALO BY THE DISK (2009, background): “The contribution of the halo to this process has been included in previ- ous studies (Hayashi et al. 2003; Kazantzidis et al. 2004b; Read et al. 2006; Peñarrubia et al. 2008; Muñoz et al. 2008) but generally not that from the luminous galaxy (but see Taylor & Babul 2001).”
The Observed Properties of Dark Matter on Small Spatial Scales (2007, background): “More generally Read et al. (2006a) provide an extensive discussion and introduction to the literature.”
Understanding the shape and diversity of dwarf galaxy rotation curves in ΛCDM (2016, methodology): “Briefly, we set up equilibrium isolated dwarf galaxies following Read et al. (2006).”
Can feedback solve the too-big-to-fail problem? (2013, background): “We have not considered the effects of subsequent evolution, including stripping from ram pressure and tides, that may be important for some Milky Way subhalos (Read et al. 2006; Brooks & Zolotov 2012; Zolotov et al. 2012; Arraki et al. 2012).”
Dark matter heats up in dwarf galaxies (2018, background): “Secondly, tidal shocking and stripping can lower the central DM density of the dwarfs, inducing scatter in ρDM(150 pc) at a fixed M∗ (e.g. Hayashi et al. 2003; Kazantzidis et al. 2004; Read et al. 2006a).”
A BARYONIC SOLUTION TO THE MISSING SATELLITES PROBLEM (2012, background): “However, tidal stripping in a cuspy halo by itself does not reduce the central densities of the most massive subhalos enough to bring them into agreement with the observed kinematics of the MW satellites (Read et al. 2006a; Boylan-Kolchin et al. 2012).”