tral kiloparsec as a light excess that may be
due to a nuclear stellar disk. The observations
were very short, only seven minutes. The key
to the measurement was the spatial resolution to probe the innermost arcsecond. More
information about this work is posted at the
Gemini website, and full results are published
in The Astrophysical Journal.
The Fastest Quasar
Ultraviolet Wind
This exceptional example, called SDSS
J023011.28
+
005913.6 or J0230 for
short, is also interesting in showing a second strong component, with an outflow
velocity around 40,000 kilometers per
second. The multiple observations of the
quasar at various times show variability
(on timescales as short as 10 days in the
quasar rest frame; Figure 4) and enable
the team to rule out some simple models
of bulk motion. Instead, they show that
some more complex geometric configurations are consistent with the observations — namely a “crossing disk” model
(of a circular cloud that crosses a circular emitting region) and “flow tube” (where a
spatially extended absorbing region passes in
front of the emitting region) for the faster and
slower outflows, respectively.
April 2016
GMOS-South image
of the center of the
Abell 85 galaxy cluster,
which shows that the
brightest cluster galaxy
at the center does
not contain the most
massive known black
hole in the Universe,
contrary to previous
estimates.
Continued study of the larger sample of about
100 candidates may reveal more systematic
characteristics of the broad absorption features and their origin. This work is featured
on the Gemini website, and full results are
published in Monthly Notices of the Royal Astronomical Society (viewable here).
Quasar winds may be fundamental to the
growth of black holes and the evolution of
galaxies, being an intimate part of the feedback mechanism that regulates black holes
and stellar growth over cosmic time. Jesse
Rogerson (York University, Canada) and collaborators have discovered an extreme example, the fastest ultraviolet wind, whose velocity approaches 20% of the speed of light.
The researchers originally used the Sloan Digital Sky Survey to find quasars that show new
broad absorption line troughs. Further observations using the Gemini Multi-Object Spectrograph (GMOS) at both Gemini North and
Gemini South show spectral changes over
time in this case. At a redshift of z = 2.47, the
galaxy’s rest frame ultraviolet emission appears at optical wavelengths, and broad CIV
absorption is the key feature the team traced.
Figure 3.
Figure 4.
Three GMOS (North
and South) spectra
obtained at different
times of the z =2.47
quasar J0230 show
the variability of the
absorption features,
especially the CIV
near rest-frame
wavelength 1550 Å.
The spectra have been
normalized based on
measurements in the
shaded regions.
Nancy A. Levenson is Deputy Director and Head
of Science at Gemini Observatory and can be
reached at: [email protected]
GeminiFocus
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