The Core-collapse Supernova Rate Problem, or the fact that we
don’t see as many core-collapse supernovae as we would expect, has a
solution, thanks to research using the Gemini South telescope. The
research team concludes that the majority of core collapse supernovae,
exploding in luminous infrared galaxies, have previously not been found
due to dust obscuration and poor spatial resolution.
Core-collapse supernovae are spectacular explosions that mark the
violent deaths of massive stars. An international team of astronomers,
led by PhD student Erik Kool of Macquarie University in Australia, used
laser guide star imaging on the Gemini South telescope to study why we
don’t see as many of these core-collapse supernovae as expected. The
study began in 2015 with the Supernova UNmasked By InfraRed detection
(SUNBIRD) project which has shown that dust obscuration and limited
spatial resolution can explain the small number of detections to date.
In this, the first results of the SUNBIRD project, the team discovered
three core-collapse supernovae, and one possible supernova that could
not be confirmed with subsequent imaging. Remarkably, these supernovae
were spotted as close as 600 light years from the bright nuclear regions
of these galaxies – despite being at least 150 million light years from
the Earth. “Because we observed in the near-infrared, the supernovae
are less affected by dust extinction compared to optical light,” said
Kool.
According to Kool the results coming from SUNBIRD reveal that their new
approach provides a powerful tool for uncovering core-collapse
supernova in nuclear regions of galaxies. They also conclude that this
methodology is crucial in characterizing these supernova that are
invisible through other means. Kool adds, “The supernova rate problem
can be resolved using the unique multi-conjugate adaptive optics
capability provided by Gemini, which allows us to achieve the highest
spatial resolution in order to probe very close to the nuclear regions
of galaxies.” This work is published in the Monthly Notices of the Royal Astronomical Society.
This research is also highlighted in the January 2018 GeminiFocus (p.11).
Abstract:
Source: Gemini Observatory
Abstract:
Core collapse supernova (CCSN) rates suffer from large uncertainties as
many CCSNe exploding in regions of bright background emission and
significant dust extinction remain unobserved. Such a shortfall is
particularly prominent in luminous infrared galaxies (LIRGs), which have
high star formation (and thus CCSN) rates and host bright and crowded
nuclear regions, where large extinctions and reduced search detection
efficiency likely lead to a significant fraction of CCSNe remaining
undiscovered. We present the first results of project SUNBIRD
(Supernovae UNmasked By InfraRed Detection), where we aim to uncover
CCSNe that otherwise would remain hidden in the complex nuclear regions
of LIRGs, and in this way improve the constraints on the fraction that
is missed by optical seeing-limited surveys. We observe in the
near-infrared 2.15 µm Ks-band, which is less affected by dust extinction
compared to the optical, using the multi-conjugate adaptive optics
imager GeMS/GSAOI on Gemini South, allowing us to achieve a spatial
resolution that lets us probe close in to the nuclear regions. During
our pilot program and subsequent first full year we have discovered
three CCSNe and one candidate with projected nuclear offsets as small as
200 pc. When compared to the total sample of LIRG CCSNe discovered in
the near-IR and optical, we show that our method is singularly effective
in uncovering CCSNe in nuclear regions and we conclude that the
majority of CCSNe exploding in LIRGs are not detected as a result of
dust obscuration and poor spatial resolution.
