連馬修 Lehner, Matthew
RCUH Research Fellow / Chief Scientist TAOS-2
辦公室Univ. of Pennsylvania
電子信箱:
mlehner
asiaa.sinica.edu.tw
研究興趣
I am interested in the outer Solar System, particularly the region
from the Kuiper Belt out to the Oort Cloud. Kuiper Belt Objects (KBOs)
smaller than about 30 km in diameter are practically invisible to
direct observational surveys, as are nearly all objects expected to
exist beyond 100 AU. I worked on The Taiwanese-American Occultation
Survey (TAOS), which
searched for occultations of distant stars by small outer Solar System
objects. Such events are rare and extremely short in duration, so we
monitored a large number of stars (typically 500 stars at any given
time) at a high exposure rate (5 Hz). We operated the survey for seven
years, and no events were found, allowing us to place the strongest
upper limits to date on the surface density of Kuiper Belt objects
with diameters between 500 meters and 30 km. Furthermore, we have also
found no objects at distances between 100 and 1000 AU, placing the
strongest upper limits to date on objects at these distances.
We have nearly completed development of a successor survey, the
Transneptunian Automated Occultation Survey
(TAOS II), which will
be more than a factor of 100 more sensitive than TAOS. The survey is
designed to monitor 10,000 stars at a rate of 20 Hz. To achieve this
goal, we will use larger telescopes and custom cameras capable of the
high readout rate. The three telescopes will are 1.3 m F/4 telescopes
with a 2.3 sq. deg. field of view. The cameras will be mosaics of
back-illuminated CMOS devices. The telescopes were installed at the
San Pedro Mártir Observatory in Baja California, México in the autumn
of 2017. The cameras will be delivered in the spring of 2018, and we
expect to begin science operations in the summer of 2018.
I am also a member of the Outer Solar System Origins Survey (OSSOS), a large program of the
Canada France Hawaii Telescope. The survey has covered 168
sq. deg. with the goal of detecting and classifying over 1,000 KBOs
down to a magnitude limit of r'=24.5. I am mainly working on follow-up
observation of the objects detected by OSSOS, primarily using the
Subaru and Gemini North telescopes. The goal of these follow-up
observations is to measure light curves and colors of the OSSOS KBOs
in order to correlate surface, shape, and rotational properties with
dynamical classification.
Finally, I am a member of the Hyper Suprime-Cam Subaru Strategic
Program (HSC SSP). This
survey comprises three components with different combinations of sky
coverage and limiting magni- tude. The wide survey will cover 1400
sq. deg. down to magnitude r'=26, the deep survey will cover 27
sq. deg. down to r'=27, and the ultradeep survey will cover 3.5
sq. deg. down to r'=28. This program is not optimized for detection of
KBOs, but a preliminary analysis of 221 sq. deg. of data from the wide
survey has succeeded in discovering 231 previously unknown objects,
with magnitudes as faint as r' = 25.3. Both the survey and analysis
are ongoing, and this work will eventually result in a very accurate
measurement of the KBO size distribution for objects with magnitudes
27>r'>25.
