Dynamically Tagged Groups of Very Metal-poor Halo Stars from the HK and Hamburg/ESO Surveys

We analyze the dynamical properties of ?1500 very metal-poor (VMP; [Fe/H] ? ?2.0) halo stars, based primarily on medium-resolution spectroscopic data from HK and Hamburg/ESO surveys. These data, collected over past 30 yr, are supplemented by a number calibration stars other small samples, along with astrometric information Gaia DR2. apply clustering algorithm to 4D energy-action space sample, identify set 38 dynamically tagged groups (DTGs), containing between 5 member stars. Many these DTGs can be associated previously known prominent substructures such as Gaia-Sausage/Enceladus (GSE), Sequoia, Helmi Stream (HStr), Thamnos. Others identified smaller streams. 10 new well, many which have strongly retrograde orbits. also investigate possible connections our ?300 individual r-process-enhanced (RPE) recent literature compilation. find that several objects similar GSE (5), HStr (4), Sequoia (1), Rg5 indicating their progenitors might been important sources RPE in Galaxy. Additionally, newly shown at least two each (DTG-2: 3, DTG-7: 2; DTG-27: 2). Taken whole, results consistent ultra-faint and/or dwarf spheroidal galaxies birth environments r-process nucleosynthesis took place, then were disrupted Milky Way.