Speaker
Description
Mass-loss from asymptotic giant branch and red supergiant stars drive
local galactic chemical evolution, but one of the main uncertainties
in quantifying this process is the spatial and temporal variations in
mass-loss across the evolved star population. A large sample of
sources is needed to recover the statistical mass-loss rate, and
variation thereof, as a function of observable stellar parameters.
We will describe a volume-limited sample of nearby evolved stars that
the Nearby Evolved Stars Survey (NESS) team is building. The program
started with initial data from a James Clerk Maxwell telescope (JCMT)
large program, where CO 3-2 and 2-1 observations were obtained for all
known AGB stars in the Solar Neighborhood, within a radius of 2 kpc.
We will focus on the current efforts being done using the group's
interferometric observations from the Atacama Large
Millimeter/submillimeter Array (ALMA). The data is bringing the
ability of the JCMT at the largest angular scales with those of the
angular resolution of ALMA's Atacama Compact Array (ACA) to probe
their circumstellar envelopes. We are interested in the mass-loss
histories, geometries, and 12C/13C and dust-to-gas ratios in order to
make predictive estimates for stellar evolution models and quantify
the dust and molecular inventory AGB stars return to the interstellar
medium. In this talk we will present preliminary results based on
roughly half of the ACA observations available, including detection
rates of the CO lines, angular extensions of the envelopes, and
general statistical properties of the sample's data. We will also
present physical parameters, including mass loss rates, that can be
obtained from the observations.
