TPF-I SWG Report - Exoplanet Exploration Program - NASA

C HAPTER 3
Figure 3-6. (Left panel) Astrometric positions and orbital fits for eight stars that show
accelerated proper motion within the central 0.8” × 0.8” of the Galaxy (Ghez et al. 2003).
(Right panel) Astrometric positions for a simulated sample of 100 stars detectable with
TPF-I. Motions are over a 10-yr baseline assuming ten observations per year per star.
to silicate particles and SiC grain as well as spectral lines from other atomic and molecular species. IRAS
detected more than 10 5 new AGB candidates. The improved spectral resolution of ISO and Spitzer
allowed the study of the AGB population of the Magellanic Clouds and other Local Group galaxies at
mid-infrared wavelengths.
Darwin/TPF-I will detect the circumstellar envelope of AGB stars located well beyond the Local Group
where these stars are being found photometrically as galaxy members (e.g., in the Sculptor group at 2.5
Mpc and in the M81 group at 4 Mpc). Furthermore, Darwin/TPF-I will provide detailed maps of the
distribution dust and gas within the envelopes of AGB stars within the Galaxy. This will be essential
information to tie basic stellar parameters to the properties of mass-loss. This is not only important for the
usage of the properties of mass loss for addressing key astrophysical questions (see above), but also to
advance theoretical models (e.g. Sandin and Hofner 2003) that cannot predict mass-loss rates from stellar
parameters. The later is largely due to the complicated physics of the interplay of stellar pulsation, shock
waves, dust formation and radiation pressure which combined all drive the mass-loss.
3.2.3 Formation, Evolution, and Growth of Black Holes
How do black holes form Do they form first, and trigger the birth of galaxies around them, or do
galaxies form first and stimulate the formation of black holes How do black holes grow Do they grow
in a merger tree as galaxies collide, or do they accumulate their mass by hydrodynamic accretion from
surrounding gas and stars in a single galaxy TPF-I will image the circum-nuclear disks of systems such
as M106 (NGC 4258). The H 2 O maser disk in that galaxy requires significant IR pumping near 10 µm—
thus its disk will be very bright. TPF-I will compliment ELT imaging. The high contrast between the
AGN and the disk requires high-fidelity imaging: TPF-I will enable a search for the dominant mode of
AGN feeding and probe the launch and collimation regions of AGN jets.
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