Guilin Liu and Nadia L. Zakamska
Quasar Feedback and
Galactic-scale Outflows
Using the Gemini Multi-Object Spectrograph at Gemini North, an international
team detected extended ionized gas nebulae around powerful radio-quiet
quasars. These ground-breaking observations provide strong evidence that
quasars in their most common mode can drive gas outflows engulfing an
entire galaxy.
One of the most fascinating astronomical discoveries of the last several decades was the
gradual realization that almost every massive galaxy, including our own Milky Way, contains
a supermassive black hole in its center. Several lines of evidence suggest a fundamental connection between the black holes residing in galaxy centers and the formation and evolution
of their host galaxies. One such observation is the tight correlation between the black hole
masses and the velocity dispersions of their host bulges. Another is the close similarity of the
black hole accretion history and the star formation history over the lifetime of the universe.
In addition to these observations, modern galaxy formation theory strongly suggests that
black hole activity has a controlling effect on shaping the host galaxy’s global properties. This
is especially true for the most massive galaxies, whose numbers decline much more rapidly
with luminosity than the predictions of large-scale dark matter simulations would suggest.
One possible explanation for this is that the black hole’s energy output, in its most active
(“quasar”) phase, may be somehow coupled to the gas from which the galaxy’s stars form.
If the quasar launches a wind that entrains and removes gas from the galaxy, or reheats the
gas, then it can shut off star formation in its host. Thus, quasars could be instrumental in
limiting the maximal mass of galaxies.
December2012
GeminiFocus
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