Milky Way Mapper

Milky Way Mapper (MWM) is a multi-object spectroscopic survey, that will provide near-infrared spectra of more than 6 million stars, to create a unique global Galactic map that encompasses the evolutionary record of the Milky Way contained in its stars and interstellar material. The entire hierarchy of structure will be sampled throughout the disk- and bulge-dominated regions of the Milky Way, which will include high quality spectra of stars and interstellar spectral lines. This data will help to quantitatively test models of the most uncertain galaxy formation physics (e.g., Rix & Bovy 2013; Bland-Hawthorn & Gerhard 2016). MWM will make use of the APOGEE spectrographs, offering a spectral resolution of R ~ 22,500 and a wavelength coverage of 1.51 – 1.70 μm. MWM will observe with the 2.5m telescopes at Apache Point and Las Campanas Observatories, employing the robotic fiber-positioning system currently under development for SDSS-V.


Midplane target surface density of the recent <a href="/dr14/irspec/">APOGEE DR14 catalog</a> (left), and the MWM’s Galactic Genesis Survey (right). The maps show a face-on schematic of the Milky Way (image credit: NASA/JPL-Caltech/R. Hurt) beneath target density contours.
Midplane target surface density of the recent APOGEE DR14 catalog (left), and the MWM’s Galactic Genesis Survey (right). The maps show a face-on schematic of the Milky Way (image credit: NASA/JPL-Caltech/R. Hurt) beneath target density contours.

Science Goals

The ecosystem of stars, gas, dust, and dark matter in large galaxies like the Milky Way has been shaped over billions of years, by various physical processes, operating over various spatial and temporal scales. MWM takes advantage of our unique perspective without our own Galaxy to create a unique global map of the Milky Way. There are three programs included in the MWM survey: the Galactic Genesis Survey, the Stellar Astrophysics program, and the Stellar System Architecture program. In addition to infra-red spectra, MWM will also observe some of its targets with the optical BOSS spectrographs.

The Galactic Genesis Survey (GGS) will produce the first spectroscopic stellar map that is contiguous, densely sampled, and all-sky, but focused on the low Galactic latitudes where most stars lie. SDSS-V will significantly expand the spectroscopic census of young stars painting a global picture of the recent Galaxy. Galactic Genesis Survey will collect infrared spectra from more than 5 million stars across the full sky, which will provide tools to address numerous questions like the dominant formation mechanisms of the Milky Way, hierarchical accretion, radial migration, and the place of the Milky Way in a cosmological context.

Both the Stellar Astrophysics (SA) and Stellar System Architecture (SSA) programs take advantage of the panoptic spectral capabilities of SDSS-V, offered by the robotic fiber-positioning system. The goal of these programs is to consistently and comprehensively measure mass, age, chemical composition, internal structure, rotation, and the presence of companions for vast samples of stars across the color-magnitude diagram. The SA program will include observations of giant stars with asteroseismic detections, massive stars, white dwarfs, deeply embedded star clusters, and a volume-limited sample of stars within 100 pc. The SSA program will target tens of thousands of multi-body systems.

More details on the Milky Way Mapper and an extended description of its science goals can be found in the SDSS-V White Paper SDSS-V: Pioneering Panoptic Spectroscopy.


Stellar astrophysical targets for MWM. The wide range of ages of the red giants provides a perfectly suited exploration space, given that their asteroseismic-calibrated ages can be determined. The luminous hot stars (upper left) ionise the gas targetted by <a href="/future/lvm">LVM</a> in the Milky Way, while the cool dwarfs (lower right) are perfect hunting grounds for rocky planets in the habitable zone. Stars marked in bright colours are located within 100 pc of the Sun, and part of MWM’s solar neighbourhood consensus. Grey points with M<sub>J</sub> > 10 are white dwarfs with <a target="_blank" href="https://www.cosmos.esa.int/web/gaia/dr1">Gaia data release 1</a> distances.
Stellar astrophysical targets for MWM. The wide range of ages of the red giants provides a perfectly suited exploration space, given that their asteroseismic-calibrated ages can be determined. The luminous hot stars (upper left) ionise the gas targetted by LVM in the Milky Way, while the cool dwarfs (lower right) are perfect hunting grounds for rocky planets in the habitable zone. Stars marked in bright colours are located within 100 pc of the Sun, and part of MWM’s solar neighbourhood consensus. Grey points with MJ > 10 are white dwarfs with Gaia data release 1 distances.

Contact information

For more information on the Milky Way Mapper, contact the SDSS-V Program Head for Stars & the Milky Way, Jennifer Johnson (Ohio State University), johnson.3064@osu.edu.