Figure 4.
The location of broad
Hb emission (measured
in light-days, from
reverberation mapping)
versus 1-micron
continuum luminosity.
Previous observations
are plotted in black,
new results are shown
in red, and upper limits
result when the host
galaxy dominates the
emission (green). The
different lines show fits
obtained using various
techniques, all of which
are consistent with a
slope of 0.6±0.1.
cation of fixed ionizing flux). Reverberation
mapping at optical wavelengths establishes
this relationship, where the continuum variability is observed after a delay in the broad
line emission. This technique has the disadvantage of being observationally timeconsuming, and fewer than 50 AGN have
been measured. Once the radius-luminosity
relationship is established, however, further
measurements are observationally easier.
This new work provides the observational
correlations in the NIR, using observations
with the Gemini Near-infrared Spectrograph
(GNIRS). This wavelength regime offers advantages over the optical and ultraviolet,
including being less contaminated by host
galaxy stellar emission, having lines that are
less confused by blending, and being less affected by dust obscuration. The sample is restricted to galaxies that have reverberation
mapping results, and the new data especially help to fill out the high-luminosity range.
based on previous measurements, and
the NIR provides the luminosity, L. The observed scatter and lack of change with the
enlarged sample here suggest that some
of the scatter is intrinsic to the relationship,
not measurement uncertainty. With a direct
measurement of the velocity spread from
the width of Paschen a or b lines, the black
hole mass can be calculated.
Alternatively, the combination of NIR luminosity and line width together can be related to the previously measured black hole
mass. The complete paper, to be published
in Monthly Notices of the Royal Astronomical
Society, provides the resulting quantitative
relationships, including consideration of
different techniques for determining the
velocity spread. A preprint is available at:
http://arxiv.org/abs/1303.1923
Nancy A. Levenson is Deputy Director and Head
of Science at Gemini Observatory and can be
reached at: [email protected]
Figure 4 shows the resulting radius-luminosity relationship, where the radius, R, is
April2013
GeminiFocus
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