Richard McDermid and Tim Davis
Jets from AGN Quench Star
Formation in Shocking Ways
Gemini Multi-Object Spectrograph Integral field unit observations of the nearby
lenticular galaxy NGC 1266 have shed light on a mysterious process that
quenches star formation in galaxies. The data reveal how jets from an active
galactic nucleus can shock and disrupt the interstellar medium, driving gas from
the galaxy and exhausting the fuel necessary to create new stars.
Figure 1.
Although galaxies come in all sizes and
shapes, their colors appear strongly
bimodal. Active star-forming galaxies
have blue optical colors because bright
young stars abound in their disks. On
the opposite end of the spectrum,
red light from cooler old stars tend to
dominate the more quiescent systems.
It is not, however, a uniform distribution from one color class to the other.
In a diagram of galaxy color versus total galaxy brightness, we see not only a
”blue cloud” of star-forming galaxies at
one end, and a tight ”red sequence” of
quiescent objects at the other, but also
what’s known as a ”green valley” of less numerous transition objects in between.
B–V and R-band
composite three-color
image of lenticular
galaxy NGC 1266. The
white bar shows a linear
scale of 1 kiloparsec;
65.94 arcseconds at an
adopted distance of
29.9 Mpc. Overlaid is
the total field-of-view
of SAURON IFU (red)
and GMOS IFU (blue)
observations.
Image credit:
SINGS Survey
This strongly bimodal color distribution wouldn’t appear so pronounced if blue-cloud galaxies are left to consume their gas via star formation and redden naturally. The color bimodality therefore implies that some galactic-scale process must actively quench star formation,
removing its fuel from the environment in one violent episode.
December2012
GeminiFocus
17