A QUANTITATIVE EXPLANATION OF THE OBSERVED POPULATION OF MILKY WAY SATELLITE GALAXIES

By Sergey E. Koposov, Jaiyul Yoo, Hans-Walter Rix, D. Weinberg, A. Macciò, J. R. M. P. I. F. Astronomy, Heidelberg, Heidelberg · Germany, I. O. Astronomy, Cambridge and 11 more. 2009

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We revisit the well known discrepancy between the observed number of Milky Way (MW) dwarf satellite companions and the predicted population of cold dark matter (CDM) subhalos, in light of the dozen new low-luminosity satellites found in imaging data from the Sloan Digital Sky Survey (SDSS) and our recent calibration of the SDSS satellite detection efficiency, which implies a total satellite population far larger than these dozen discoveries. We combine a detailed dynamical model for the CDM subhalo population with simple, physically motivated prescriptions for assigning a stellar content to each subhalo, then apply observational selection effects and compare to the current observational census. Reconciling the observed satellite population with CDM predictions still requires strong mass-dependent suppression of star formation in low-mass subhalos: models in which the stellar mass is a constant fraction F*(Ωb/Ωm) of the subhalo mass Msat at the time it becomes a satellite fail for any choice of F*. However, previously advocated models that invoke suppression of gas accretion after reionization in halos with circular velocity Vcirc ⩽ Vcrit ≈ 35 km s−1 can reproduce the observed satellite counts for −15 ⩽ MV ⩽ 0. Successful models require F* ≈ 10−3 in halos with Vcirc>Vcrit and strong suppression of star formation before reionization in halos with Vcirc ≲ 10 km s−1; models without pre-reionization suppression predict far too many satellites with −5 ⩽ MV ⩽ 0. In this successful model, the dominant fraction of stars formed after reionization at all luminosities. Models that match the satellite luminosity distribution also match the observed heliocentric radius distribution, and they reproduce the observed characteristic stellar velocity dispersion σ* ≈ 5–10 km s−1 of the SDSS dwarfs given the observed sizes (∼50–200 pc) of their stellar distributions. The model satellites have M(<300 pc) ∼ 107 M☉ as observed even though their present-day total halo masses span more than two orders of magnitude; the constancy of central masses mainly reflects the profiles of CDM halos. Our modeling shows that natural physical mechanisms acting within the CDM framework can quantitatively explain the properties of the MW satellite population as it is presently known, thus providing a convincing solution to the “missing satellite” problem.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0ad6d8056103d9878adc001df7d2c540d117c8e2

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Citations in the corpus

Subhaloes in self-interacting galactic dark matter haloes (2012, background): “…to be a more serious challenge than the well known excess of DM subhaloes compared to the number of observed MW satellites, pointed out over a decade ago (Klypin et al. 1999; Moore et al. 1999), and that has a viable solution based on the quenching of star formation (e.g. Koposov et al. 2009).”
Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation (2014, background): “Alternatively hundreds of dark-matter ultra-faint satellite galaxies have been predicted within the framework of the SMoC to surround the MW spheroidally ( [93, 209], Sec.”
THE QUENCHING OF THE ULTRA-FAINT DWARF GALAXIES IN THE REIONIZATION ERA (2014, background): “…formation in the smallest DM sub-halos QUENCHING OF THEULTRA-FAINT DWARF GALAXIES 11 (e.g., Bullock et al. 2001; Ricotti & Gnedin 2005; Muñoz et al. 2009; Bovill & Ricotti 2009, 2011a, 2011b; Tumlinson 2010; Koposov et al. 2009; Li et al. 2010; Salvadori & Ferrara 2009; Salvadori et al. 2014).”
Galactic stellar haloes in the CDM model (2009, result): “In agreement with previous studies using semi-analytic models and lower-resolution N-body simulations (Macciò, Kang & Moore 2009; Li et al. 2009; Koposov et al. 2009; Busha et al. 2010), and N-body gasdynamic simulations (Okamoto & Frenk 2009), we find that this characteristic scale arises…”
Too big to fail? The puzzling darkness of massive Milky Way subhaloes (2011, background): “…galaxies correspond to subhaloes that were the most massive at some earlier time (Bullock et al. 2000; Kravtsov et al. 2004b; Ricotti & Gnedin 2005; Koposov et al. 2009; Okamoto & Frenk 2009; Busha et al. 2010), often the epoch of reionization, with galaxy formation strongly suppressed in lower…”
The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology (2012, unknown): “…papers: Dekel & Silk (1986); Dekel & Woo (2003); Tollerud et al. (2008); D’Onghia & Lake (2008); Li & Helmi (2008); Macciò, Kang & Moore (2009); Koposov et al. (2009); Okamoto& Frenk (2009); Kirby et al. (2009); Shaya et al. (2009); Busha et al. (2010); Primack (2009); Macciò & Fontanot…”
The Milky Way’s bright satellites as an apparent failure of ΛCDM (2011, background): “…halo (Stoehr et al. 2002; Hayashi et al. 2003; Peñarrubia et al. 2008), and those that assume satellites form only in the biggest halos defined at some earlier epoch, e.g., reionization (Bullock et al. 2000; Kravtsov et al. 2004b; Ricotti & Gnedin 2005; Koposov et al. 2009; Okamoto & Frenk 2009).”
THE SPLASH SURVEY: SPECTROSCOPY OF 15 M31 DWARF SPHEROIDAL SATELLITE GALAXIES (2011, background): “The missing satellite problem noted above is the classic example, for which a variety of solutions have surfaced (e.g, Bullock et al. 2000; Strigari et al. 2007; Tollerud et al. 2008; Bovill & Ricotti 2009; Koposov et al. 2009; Kravtsov 2010).”
Too big to fail in the Local Group (2014, background): “…AM relationships at higher masses, one obtains stellar mass functions that agree well with those of the MW and M31 satellites for M 105 M (Koposov et al. 2009; Busha et al. 2010; Kravtsov 2010; Boylan-Kolchin, Bullock & Kaplinghat 2012; C© 2014 The Authors Published by Oxford University…”
Accurate masses for dispersion-supported galaxies (2009, methodology): “This general behavior is difficult to reproduce in models constructed to confront the Milky Way satellite population (e.g., Koposov et al. 2009; Li et al. 2009; Macciò et al. 2009; Muñoz et al. 2009; Salvadori & Ferrara 2009; Busha et al. 2010; Kravtsov 2010), which typically predict a noticeable…”
Bent by baryons: the low-mass galaxy-halo relation (2014, background): “It can be an important factor in establishing the number of observable dwarf galaxies in the local universe (e.g. Kauffmann et al. 1993; Bullock et al. 2000; Benson et al. 2002; Somerville 2002; Koposov et al. 2009; Okamoto & Frenk 2009).”
Local-Group tests of dark-matter concordance cosmology - Towards a new paradigm for structure formation (2010, background): “…have a severe substructure problem as there would not be any satellites with DM halos less massive than about 1010 M⊙ with stars, in conflict with DM predictions provided by, e.g., Knebe et al. (2008), Diemand et al. (2008), Busha et al. (2010), Macciò et al. (2010), and Koposov et al. (2009).”
BEASTS OF THE SOUTHERN WILD: DISCOVERY OF NINE ULTRA FAINT SATELLITES IN THE VICINITY OF THE MAGELLANIC CLOUDS (2015, background): “In other words, today’s semi-analytic models are so flexible they can easily produce any number of Milky Way (MW) satellites: from a few tens up to several thousands (e.g. Koposov et al. 2009).”
WHY BARYONS MATTER: THE KINEMATICS OF DWARF SPHEROIDAL SATELLITES (2012, methodology): “3 For stellar masses above 106 M⊙, this relation is in agreement with commonly adopted relations in the literature, (e.g., Koposov et al. 2009; Kravtsov 2010; Rashkov et al. 2012; Sales et al. 2013).”
CHEMICAL EVOLUTION IN HIERARCHICAL MODELS OF COSMIC STRUCTURE. II. THE FORMATION OF THE MILKY WAY STELLAR HALO AND THE DISTRIBUTION OF THE OLDEST STARS (2009, result): “These basic results are in agreement with other recent attempts to explain the luminosity function of MW satellites in semi-analytic models (Koposov et al. 2009; Maccio et al. 2009).”
The current status of galaxy formation (2012, background): “The ultrafaint dwarfs in the MW may be fossils of these first galaxies (as checked by detailed models Koposov et al., 2009; Salvadori & Ferrara, 2009; Bovill & Ricotti, 2011).”
The impact of dark matter cusps and cores on the satellite galaxy population around spiral galaxies (2010, result): “This is in remarkable contrast with the number of known satellite galaxies in the MW, which to date adds up to a mere couple of dozens (e.g. Belokurov et al. 2007; Koposov et al. 2009).”
THE VELOCITY FUNCTION IN THE LOCAL ENVIRONMENT FROM ΛCDM AND ΛWDM CONSTRAINED SIMULATIONS (2009, background): “…suppression of galaxy formation in small mass halos and lead to the solution of the problem (Somerville 2002; Benson et al. 2002b,a; Gnedin & Kravtsov 2006; Koposov et al. 2009), it is also possible to alleviate the discrepancy by adopting alternative models with a different type of dark matter.”
Cosmic Dawn (CoDa): the first radiation-hydrodynamics simulation of reionization and galaxy formation in the Local Universe (2015, methodology): “In this framework, a number of semi-analytical models (hereafter SAMs) have been shown to reproduce well the satellite population of the Milky Way (hereafter MW), such as Koposov et al. (2009); Muñoz et al. (2009); Busha et al. (2010); Macciò et al. (2010); Li et al. (2010); Font et al. (2011).”