Searching for Dwarf Satellites around Milky Way – Analog Galaxies with the SAGA survey
Ben Weiner, Steward Observatory
Dwarf satellites of massive galaxies are a probe of many issues in galaxy evolution and cosmology, including the nature of low-mass galaxies, star formation at early times, accretion into halos, and the abundance of low-mass dark matter halos. Much attention has been devoted to the number and nature of Milky Way and M31 dwarf satellites, especially the “missing satellites problem.” However, we know very little about dwarf satellites outside the Local Group below the mass of the LMC, and we don’t know if the MW and M31 satellite systems are typical. The SAGA (Satellites Around Galactic Analogs) survey collaboration aims to address this with both observational and theoretical studies of satellite abundances and properties around Milky Way analog central galaxies. I will present results from our MMT/Hectospec wide field spectroscopic surveys for satellites. We have surveyed the fields of several nearby galaxies that are similar to the Milky Way to detect and spectroscopically confirm dwarf satellites. We find a range of numbers of satellites, suggesting that there is a significant variance in halo histories. We also find that not all dwarf systems resemble the Milky Way and M31 systems. I will discuss these results and some of the implications on the life cycle of satellites that we can infer from satellite abundances and properties, including their images and spectra.
Why Space Weather Matters and How Forecasting Will Improve in the DSCOVR Era
Doug Biesecker, NOAA/NWS/Space Weather Prediction Center
Space Weather is a growing enterprise, with growing recognition of its importance inside and outside government. The largest concern is with the electric power grid, but impacts to Global Positioning Systems (GPS) are also significant. Other areas of impact include satellites and human space flight, and high frequency communication for aviation, mariners, and emergency responders, among many. The NOAA National Weather Service’s Space Weather Prediction Center (SWPC) is the nation’s official source of space weather watches, warnings and alerts. SWPC does this with a 24×7 staffed operation that monitors the Sun, solar wind, and geospace environment taking advantage of a broad suite of observations and models to provide the best forecasts possible. In conjunction with the growing recognition of space weather, NOAA launched its first mission, the Deep Space Climate Observatory (DSCOVR), out of the Earth’s orbit to an orbit about the L1 Lagrange point. This is also NOAA’s first satellite mission where space weather is the primary mission and DSCOVR marks the first of what is expected to be a long series of space weather monitoring satellites. NOAA is also bringing numerical space weather models into the mix of models running on the nation’s supercomputers. Numerical space weather models have demonstrated the ability to improve the onset time of space weather storms and will, for the first time, allow regional geomagnetic forecasting. Instead of describing conditions on Earth with a single number, customers will have forecasts tailored to their location.