Figure 3.
The combined light
curve of image A
(blue), B (green), and
C (red), by shifting the
data points of A and
B by their respective
time delay and
magnification ratios:
-47.7 days and -0.34
magnitude for B, and
722 days and 0.483
magnitude for C. The
shifted light curve of C
predicts the expected
brightness of image A in
2016 and 2017. Figure
reproduced from Dahle
et al., 2015.
If C brightens significantly, as it did in 2014
and 2015, we know to expect the same magnitude of brightening in A and B about two
years later, and plan future observations for
that time.
Figure 4.
Meanwhile, our team has embarked on a
multi-wavelength monitoring campaign
aimed at studying the physical conditions
in the quasar’s host galaxy. In this program,
we will use Gemini and NOT in the optical,
This figure, reproduced
from Dahle et al.,
shows the field of SDSS
J2222 + 2745 after the
bright cluster galaxies
were modeled and
their light subtracted
from the image .This
procedure reveals
the three fainter
images (D, E, and F)
of the quasar that are
embedded in the light
of these galaxies. The
red contours show the
light distribution in the
original image.
6
and the Swift space telescope in UV and Xray, in a program awarded by the University
of Michigan. We’ll also use observations with
the HST in Cycle 22 (PI: Keren Sharon) to
compute a detailed lens model of the cluster, to further constrain the mass distribution
of the foreground lens.
The Gemini monitoring will uniquely enable
a measurement of the time delays of the
three faint images of the quasar: D, E, and F
(Figure 4). These images are much dimmer
than A, B, and C, and their detection is further
complicated by their position near the bright
galaxies at the center of the cluster. These
forthcoming measurements could shed light
on the details of the distribution of the luminous mass and dark matter at the very core of
the galaxy cluster, at a resolution that cannot
be obtained by any other method.
Keren Sharon is an astronomer and assistant
professor at the University of Michigan
astronomy department and can be reached at:
[email protected]
GeminiFocus
2015 Year in Review
January 2016