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Gaps in the GD-1 Star Stream

, : Gaps in the GD-1 Star Stream. The Astrophysical Journal 768(2): 171

GD-1 is a long, thin, Milky Way star stream that has readily visible densityvariations along its length. We quantify the locations, sizes and statisticalsignificance of the density structure, i.e. gaps, using a set of scaledfilters. The shapes of the filters are based on the gaps that develop insimulations of dark matter sub-halos crossing a star stream. The high Galacticlatitude 8.4 kpc long segment of GD-1 that we examine has 8+/-3 gaps of 99%significance or greater, with the error estimated on the basis of tests of thegap-filtering technique. The cumulative distribution of gaps more than 3 timesthe width of the stream is in good agreement with predictions for dark mattersub-halo encounters with cold star streams. The number of gaps narrower than 3times the width of the GD-1 stream falls well below the cold stream predictionwhich is taken into account for the gap creation rate integrated over allsizes. Simple warm stream simulations scaled to GD-1 show that the falloff ingaps is expected for sub-halos below a mass of 10^6 M_sun. The GD-1 gapsrequires 100 sub-halos >10^6 M_sun within 30 kpc, the apocenter of GD-1 orbit.These results are consistent with LCDM sub-halo predictions but furtherimprovements in stream signal-to-noise and gap modeling will be welcome.


DOI: 10.1088/0004-637x/768/2/171

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