The SAURON IFU data for
this object were taken as
part of the wider ATLAS3D
which attempts to understand the formation and
evolution of red-sequence
galaxies (Cappellari et al.,
2011). The SAURON data
only provide H-beta, [O III]
and faint [N I] lines — insufficient to securely characterize the ionized gas properties. We therefore used
the GMOS IFU (2-slit mode)
to obtain complementary
data around the H-alpha
line, making a mosaic of
four pointings. The coverage of the two IFU data sets
can been seen in Figure 1.
A Surprise Finding
While analyzing the data, we encountered
our first surprise: the ionized gas lines had
strange profile shapes, implying that at least
two ionized gas components exist along
each line of sight. After carefully separating
these lines to ensure a robust determination
of the ionized gas kinematics of each component, we found that one of them traced
the outflow, which emerges in the galaxy’s
polar plane. The ionized gas in this outflow
pushes outwards at speeds of up to 800 kilometers per second (kms), ensuring it will
leave its host galaxy entirely, enriching the
intergalactic medium with metals.
The second ionized gas component extends
to larger radii, and appears bound to the galaxy, but its origin is unclear. It may simply reflect unrelated gas components at different
locations along the line of sight, or it may be
a coherent rotating structure that has been
disturbed by the outflow. Figure 2 shows the
GMOS view of these components.
December2012
In addition to the ionized gas, the GMOS
data also shed light on the kinematics of the
neutral atomic gas in this system — thanks
to the detection of absorption lines caused
by sodium atoms in the gas phase, visible after careful subtraction of the stellar absorption spectrum. Alatalo et al. (2011) detected
atomic hydrogen in absorption in NGC 1266,
and our GMOS observations confirmed that
the outflow is indeed expelling neutral gas
from the galaxy at speeds up to 500 kms.
As we view the gas projected against the
galaxy’s starlight, we were able to use the
observed sodium (Na D) absorption profiles
to set constraints on the size and orientation
of the outflow. The results show well-correlated neutral and molecular outflows along
a slightly different axis to the ionized gas.
The cause of this effect is unclear.
High-resolution radio observations of NGC
1266 reveal it to have a small asymmetric
double radio jet. Alatalo et al. (2011) hypothesized that the AGN is driving this nascent
structure into the extremely dense molecular ISM surrounding it, causing the outflow.
GeminiFocus
Figure 3.
An example BPT-type
diagram — which
demonstrates
how LINERs can be
distinguished from
normal H II regions and
normal AGNs — for
the inner part of NGC
1266. The Y-axis shows
the [O III]/H-beta ratio
derived from SAURON
data, and it is plotted
versus the [S II]/H-alpha
line ratio from GMOS
observations. In the
bottom right of the plot
is the typical error bar
associated with each
point. Overplotted
are diagnostic lines,
which indicate the
dominant line excitation
mechanism.
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