THE INVISIBLES: A DETECTION ALGORITHM TO TRACE THE FAINTEST MILKY WAY SATELLITES

By Shane Walsh, B. Willman, H. Jerjen. 2008

160 citations recorded by the source corpus.

A specialized data-mining algorithm has been developed using wide-field photometry catalogs, enabling systematic and efficient searches for resolved, extremely low surface brightness satellite galaxies in the halo of the Milky Way (MW). Tested and calibrated with the Sloan Digital Sky Survey Data Release 6 (SDSS-DR6) we recover all 15 MW satellites recently detected in SDSS, six known MW/Local Group dSphs in the SDSS footprint, and 19 previously known globular and open clusters. In addition, 30 point-source overdensities have been found that correspond to no cataloged objects. The detection efficiencies of the algorithm have been carefully quantified by simulating more than three million model satellites embedded in star fields typical of those observed in SDSS, covering a wide range of parameters including galaxy distance, scale length, luminosity, and Galactic latitude. We present several parameterizations of these detection limits to facilitate comparison between the observed MW satellite population and predictions. We find that all known satellites would be detected with >90% efficiency over all latitudes spanned by DR6 and that the MW satellite census within DR6 is complete to a magnitude limit of MV ≈ −6.5 and a distance of 300 kpc. Assuming all existing MW satellites contain an appreciable old stellar population and have sizes and luminosities comparable with currently known companions, we predict lower and upper limit totals of 52 and 340 MW dwarf satellites within ∼260 kpc if they are uniformly distributed across the sky. This result implies that many MW satellites still remain undetected. Identifying and studying these elusive satellites in future survey data will be fundamental to test the dark matter distribution on kpc scales.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/d013e2e95f8996c548a1a024ce0d5f688f81c157

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Citations in the corpus

Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1 (2019, methodology): “The results of this analysis may be compared to similar analyses based on data from SDSS (e.g., Koposov et al. 2008; Tollerud et al. 2008; Walsh et al. 2009); however, recent observations suggest that a more complex modeling framework is necessary (e.g. Jethwa et al. 2018; Newton et al. 2018;…”
A KINEMATIC STUDY OF THE ANDROMEDA DWARF SPHEROIDAL SYSTEM (2013, background): “Observers have also attempted to quantify current survey completeness and radial selection effects to account for the number of satellites we are not currently able to detect (e.g., Koposov et al. 2008; Tollerud et al. 2008; Walsh et al. 2009).”
Galactic Searches for Dark Matter (2012, background): “Given that the satellite population is complete down to at least a luminosity of the classical satellites (Walsh et al., 2009), in the regime surveyed by SDSS it is no longer possible to postulate that a large population of undetected satellites exist at the same luminosity as the classical…”
EIGHT ULTRA-FAINT GALAXY CANDIDATES DISCOVERED IN YEAR TWO OF THE DARK ENERGY SURVEY (2015, methodology): “…star clusters and/or more compact stellar systems of uncertain classification were reported during roughly the same period (e.g., Koposov et al. 2007; Walsh et al. 2009; Belokurov et al. 2010, 2014; Muñoz et al. 2012; Balbinot et al. 2013; Laevens et al. 2014; Kim & Jerjen 2015a; Kim et al. 2015b).”
ACCURATE STELLAR KINEMATICS AT FAINT MAGNITUDES: APPLICATION TO THE BOÖTES I DWARF SPHEROIDAL GALAXY (2011, background): “Modelling the census of ∼ 25 known Milky Way dSphs for survey incompleteness (Koposov et al. 2008; Walsh et al. 2009), one can estimate that the number of such galaxies within the halo of the Milky Way could be several hundred, although with a significant error-bar (Tollerud et al. 2008; Koposov et…”
A STELLAR MASS THRESHOLD FOR QUENCHING OF FIELD GALAXIES (2012, background): “Ultrafaint galaxies (MV > −5, Mstellar < 10 4 M⊙) are currently detectable out to only 50 kpc in the Milky Way halo (Walsh et al. 2009).”
A BARYONIC SOLUTION TO THE MISSING SATELLITES PROBLEM (2012, background): “It is also important to consider the number of faint satellites that remain undetected due to observational incompleteness (Willman et al. 2004; Simon & Geha 2007; Tollerud et al. 2008; Walsh et al. 2009; Koposov et al. 2009; Rashkov et al. 2012).”
There's no place like home? Statistics of Milky Way-mass dark matter haloes (2009, background): “The resolution of this discrepancy likely lies in the strong dependence of galaxy formation physics on Macc (see Kravtsov 2010 for a recent review) combined with the limited sky coverage and the surface brightness detection threshold of the SDSS (Tollerud et al. 2008; Walsh et al. 2009).”
Too big to fail? The puzzling darkness of massive Milky Way subhaloes (2011, background): “…al. 2005; Belokurov et al. 2007), and it has become clear that up to a factor of ∼ 5 − 20 times as many faint galaxies could remain undetected at present owing to incomplete sky coverage, luminosity bias, and surface brightness limits (Tollerud et al. 2008; Walsh et al. 2009; Bullock et al. 2010).”
Gravitational probes of dark matter physics (2017, background): “could be hundreds (if not thousands) of satellites of the Milky Way (Figure 6) [295, 296, 297, 298, 299, 122, 123].”
BARYONS MATTER: WHY LUMINOUS SATELLITE GALAXIES HAVE REDUCED CENTRAL MASSES (2012, background): “When combined with observational incompleteness effects (Simon & Geha 2007; Tollerud et al. 2008; Walsh et al. 2009; Koposov et al. 2009), it is likely that baryonic effects can bring the predicted number of subhalos in line with the observed number of satellites.”