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We search for excess gamma-ray emission coincident with the positions ofconfirmed and candidate Milky Way satellite galaxies using 6 years of data fromthe Fermi Large Area Telescope (LAT). Our sample of 45 stellar systems includes28 kinematically confirmed dark-matter-dominated dwarf spheroidal galaxies(dSphs) and 17 recently discovered systems that have photometriccharacteristics consistent with the population of known dSphs. For each ofthese targets, the relative predicted gamma-ray flux due to dark matterannihilation is taken from kinematic analysis if available, and estimated froma distance-based scaling relation otherwise, assuming that the stellar systemsare dark-matter-dominated dSphs. LAT data coincident with four of the newlydiscovered targets show a slight preference (each ~$2 \sigma$ local) forgamma-ray emission in excess of the background. However, the ensemble ofderived gamma-ray flux upper limits for individual targets is consistent withthe expectation from analyzing random blank-sky regions, and a combinedanalysis of the population of stellar systems yields no globally significantexcess (global significance $<1 \sigma$). Our analysis has increasedsensitivity compared to the analysis of 15 confirmed dSphs by Ackermann et al.2015. The observed constraints on the dark matter annihilation cross sectionare statistically consistent with the background expectation, improving by afactor of ~2 for large dark matter masses ($m_{{\rm DM},b \bar b} \gtrsim 1$TeV and $m_{{\rm DM},\tau^{+}\tau^{-}} \gtrsim 70$ GeV) and weakening by afactor of ~1.5 at lower masses relative to previously observed limits.

Searching for Dark Matter Annihilation in Recently Discovered Milky Way Satellites with Fermi-LAT