Mass Loss from Galactic Bulge AGB stars

Margaret Meixner (STScI/ visiting Scientist at Harvard-

Smithsonian CfA) Nimesh Patel, Dave Riebel,

Ben Sargent, Sundar Srinivasan, Ken Young

Why Galactic Bulge?

•  Known Distance: 8 kpc (Reid 1993) •  Extreme environment •  High metallicity: peak at -0.3, but wide range:

-1<[Fe/H]<1 •  ISOGal studies reveal a population of AGB

star candidates suitable for followup (Omont et al.)

•  Prior studies show that all AGB stars in bulge are oxygen rich, with silicate dust features (Blommaert et al.)

ISOGal sample: spectroscopy of 107 candidate AGB stars

Schulteis et al. 2003

Metallicity of Bulge ISOGal sample

bulge

Solar neigh.

Schulteis et al. 2003

Mass Loss rate from IR

Schulteis et al. 2003

SMA project:

•  Use SMA to spatially filter the foreground CO cloud emission, and detect the point source AGB molecular winds of Galactic Bulge AGB stars.

•  Use extended SMA configuration, and observe two AGB stars per track.

•  Goal: to measure gas mass-loss rates, compare to dust mass-loss rates and estimate dust to gas mass ratios

•  Data taken last week…

Vexp Vexp V0

V0-Vexp

V0+Vexp

V0 Jy

V0 V0-Vexp V0+Vexp

Vexp

Vexp

Mass Loss rates from CO

Knapp & Morris (1985) Ramstedt et al. (2008)

Velocity integrated intensity CO abundance

Distance

Beam size

Prior work: CO detected in Galactic AGB stars/ OH-IR stars:

Winnberg et al. 2009

CO detected in Galactic AGB stars/ OH-IR stars: OH0.3-0.2

Winnberg et al. 2009

CO detected in Galactic AGB stars/ OH-IR stars: OH 359.762

Winnberg et al. 2009

Our SMA sample

Schulteis name log Mdot (IR) Type

Vstar (km/s)

Del-V (km/s)

A12 -4.65 OH 359.77+0.08 107.60 30A51 -4.73 OH 359.681-0.095 -98.70 20A10 -4.75 OH 359.598+0.00 -73.30 40A27 -4.78 AGB ? ?

Galactic Bulge: A12, OH 359.77+0.08

Galactic Bulge: A12, OH 359.77+0.08

Galactic Bulge: A51, OH 359.681-0.095

Galactic Bulge: A51, OH 359.681-0.095

Preliminary results from SMA sample

Schulteis name Comment

line flux (JyXkm/s) Mdot

A12 detected 42.5 8.3x10^-4A51 detected 32 6.24x10^-4A10 confused … ?A27 3 potential … ?

Future Prospects

•  Continue this galactic bulge project to collect larger numbers and statistics

•  This project demonstrates an approach that could be used for LMC and SMC AGB samples, but with ALMA