observing time with very little
cloud cover and excellent see-
ing (for the imaging). Unlike the
nights lost to weather in classi-
cal observing, we obtained our
data with the required sensi-
tivity despite uncooperative
weather over Maunakea.
Figure 3.
Top panel: GMOS-N
spectrum of the FRB
host galaxy (dark blue
line) shows prominent
[OIII] and H-alpha
emission lines. Other
emission lines are also
marked. The pink line
shows a neighboring
Galactic star.
Side panel: An i-band
image of the host
galaxy and the
neighboring star.
The galaxy is slightly
extended compared to
the seeing and is well fit
with a Gaussian profile.
Figures adapted from
Tendulkar et al., 2017.
6
Results
The Gemini-North imaging and spectroscop-
ic observations revealed that FRB 121102
was hosted in a low-metallicity star-forming
dwarf galaxy at a redshift of z = 0.19273(8)
— the first incontrovertible proof that FRB
121102 is at a cosmological distance (Fig-
ure 3; Tendulkar et al., 2017). The redshift is
consistent with the z < 0.3 redshift that was
estimated from the excess DM for this FRB.
If thi