313 research outputs found
Sub-Arcsecond Near-Infrared Images of Massive Star Formation Region NGC 6334 V
We present high spatial resolution (0\farcs3) polarimetric images in the
and bands and direct images in the and bands of the NGC 6334
V infrared nebulae. The images show complex structures including the
multi-shells and various knots in the nebulae. The appearances and colors of
the eastern and western nebulae differ considerably. Our polarization images
also show differences between the illuminating sources of the nebulae: the
eastern nebula is illuminated by a deeply embedded mid-infrared source, KDJ 4,
and the western nebula by our newly detected near-infrared source, WN-A1. The
degree of polarization of the nebulae is very large, up to 70% at and 60%
at , which is consistent with a single scattering of near-infrared radiation
from each source at the walls of the mass outflows
Lyot-based Low Order Wavefront Sensor: Implementation on the Subaru Coronagraphic Extreme Adaptive Optics System and its Laboratory Performance
High throughput, low inner working angle (IWA) phase masks coronagraphs are
essential to directly image and characterize (via spectroscopy) earth-like
planets. However, the performance of low-IWA coronagraphs is limited by
residual pointing errors and other low-order modes. The extent to which
wavefront aberrations upstream of the coronagraph are corrected and calibrated
drives coronagraphic performance. Addressing this issue is essential for
preventing coronagraphic leaks, thus we have developed a Lyot-based low order
wave front sensor (LLOWFS) to control the wavefront aberrations in a
coronagraph. The LLOWFS monitors the starlight rejected by the coronagraphic
mask using a reflective Lyot stop in the downstream pupil plane. The early
implementation of LLOWFS at LESIA, Observatoire de Paris demonstrated an open
loop measurement accuracy of 0.01 lambda/D for tip-tilt at 638 nm when used in
conjunction with a four quadrant phase mask (FQPM) in the laboratory. To
further demonstrate our concept, we have installed the reflective Lyot stops on
the Subaru Coronagraphic Extreme AO (SCExAO) system at the Subaru Telescope and
modified the system to support small IWA phase mask coronagraphs (< 1 lambda/D)
on-sky such as FQPM, eight octant phase mask, vector vortex coronagraph and the
phase induced amplitude apodization complex phase mask coronagraph with a goal
of obtaining milli arc-second pointing accuracy. Laboratory results have shown
the measurement of tip, tilt, focus, oblique and right astigmatism at 1.55 um
for the vector vortex coronagraph. Our initial on-sky result demonstrate the
closed loop accuracy of < 7 x 10-3 lambda/D at 1.6 um for tip, tilt and focus
aberrations with the vector vortex coronagraph.Comment: 9 pages, 9 Figures, Proc. of SPIE Astronomical Telescopes +
Instrumentation 201
On-sky demonstration of low-order wavefront sensing and control with focal plane phase mask coronagraphs
The ability to characterize exoplanets by spectroscopy of their atmospheres
requires direct imaging techniques to isolate planet signal from the bright
stellar glare. One of the limitations with the direct detection of exoplanets,
either with ground- or space-based coronagraphs, is pointing errors and other
low-order wavefront aberrations. The coronagraphic detection sensitivity at the
diffraction limit therefore depends on how well low-order aberrations upstream
of the focal plane mask are corrected. To prevent starlight leakage at the
inner working angle of a phase mask coronagraph, we have introduced a
Lyot-based low-order wavefront sensor (LLOWFS), which senses aberrations using
the rejected starlight diffracted at the Lyot plane. In this paper, we present
the implementation, testing and results of LLOWFS on the Subaru Coronagraphic
Extreme Adaptive Optics system (SCExAO) at the Subaru Telescope.
We have controlled thirty-five Zernike modes of a H-band vector vortex
coronagraph in the laboratory and ten Zernike modes on sky with an integrator
control law. We demonstrated a closed-loop pointing residual of 0.02 mas in the
laboratory and 0.15 mas on sky for data sampled using the minimal 2-second
exposure time of the science camera. We have also integrated the LLOWFS in the
visible high-order control loop of SCExAO, which in closed-loop operation has
validated the correction of the non-common path pointing errors between the
infrared science channel and the visible wavefront sensing channel with
pointing residual of 0.23 mas on sky.Comment: 12 pages, 15 figures, Accepted and scheduled for publication in
September 2015 issue of the PAS
Molecular Basis on Nitrogen Utilization in Rice(Recent Topics of the Agricultunal Biological Science in Tohoku University)
Rice (Oryza sativa L.) is the major provision for half of the world population and is the important model crop in terms of synteny. Nitrogen is a massive prerequisite element for rice during its life span. During evolutionary processes, rice has acquired strategic systems of nitrogen metabolism for the survival, i.e., the highly efficient ammonium assimilation in roots and nitrogen remobilization (nitrogen recycling). In our laboratory, research is underway to elucidate molecular mechanisms, cellular functions and the communication mechanisms in nitrogen metabolisms, especially ammonium assimilation in roots and nitrogen recycling, in rice. In this article, aim and overview of our research projects, and some recent research topics are shown
On-sky speckle nulling demonstration at small angular separation with SCExAO
This paper presents the first on-sky demonstration of speckle nulling, which
was achieved at the Subaru Telescope in the context of the Subaru Coronagraphic
Extreme Adaptive Optics (SCExAO) Project. Despite the absence of a high-order
high-bandwidth closed-loop AO system, observations conducted with SCExAO show
that even in poor-to-moderate observing conditions, speckle nulling can be used
to suppress static and slow speckles even in the presence of a brighter dynamic
speckle halo, suggesting that more advanced high-contrast imaging algorithms
developed in the laboratory can be applied to ground-based systems.Comment: 5 figures, accepted for publication by PAS
SUBARU Near-Infrared Multi-Color Images of Class II Young Stellar Object, RNO91
We conducted sub-arcsecond near-infrared imaging observations of RNO91 with
CIAO mounted on the SUBARU 8.2 m telescope. We present our JHK band data along
with optical images, which when considered together reveal a complex
circumstellar structure. We examined the colors of associated nebula and
compared the geometry of the outflow/disk system suggested by our data with
that already proposed on the basis of previous studies. Our K-band image shows
bright circumstellar nebulosity detected within 2"(300AU) around the central
source while it is less conspicuous at shorter wavelengths such as J and
optical. P.A. and size of this red color nebulosity in our H-K color image
agree with those of the previously detected polarization disk. These data
agreement indicate that this bright circumstellar nebulosity region which
follows the reddening law might be attributed to a disk-like structure. At J
and optical wavelengths, several blue knot-like structures are detected around
and beyond the bright circumstellar nebulosity. We suggest that these knotty
reflection nebulae may represent disintegrating fragments of an infalling
envelope. The three-color composite image has an appearance of arc-shaped
nebulosity extending to the north and to the east through the central source.
On the other end of this arc-shaped structure, the nebula appears to become
more extended (2."3 long) to the southwest. We interpret these structures as
roots of bipolar cavities opening to the northeast and southwest. The complex
distribution of reflection nebulosity seen around RNO91 appears to confirm the
interpretation of this source as an object dispersing its molecular envelope
while transitioning from protostar to T Tauri star.Comment: 18 pages, 6 figures, Accepted by Publications of the Astronomical
Society of Japa
SCExAO as a precursor to an ELT exoplanet direct imaging instrument
The Subaru Coronagraphic Extreme AO (SCExAO) instrument consists of a high
performance Phase Induced Amplitude Apodisation (PIAA) coronagraph combined
with an extreme Adaptive Optics (AO) system operating in the near-infrared (H
band). The extreme AO system driven by the 2000 element deformable mirror will
allow for Strehl ratios >90% to be achieved in the H-band when it goes closed
loop. This makes the SCExAO instrument a powerful platform for high contrast
imaging down to angular separations of the order of 1lambda/D and an ideal
testbed for exploring coronagraphic techniques for ELTs. In this paper we
report on the recent progress in regards to the development of the instrument,
which includes the addition of a visible bench that makes use of the light at
shorter wavelengths not currently utilized by SCExAO and closing the loop on
the tip/tilt wavefront sensor. We will also discuss several exciting guest
instruments which will expand the capabilities of SCExAO over the next few
years; namely CHARIS which is a integral field spectrograph as well as
VAMPIRES, a visible aperture masking experiment based on polarimetric analysis
of circumstellar disks. In addition we will elucidate the unique role extreme
AO systems will play in enabling high precision radial velocity spectroscopy
for the detection of small companions.Comment: 7 pages, 2 figures Proceedings of AO4ELTs3 conference, paper 13396,
Florence, Italy, May 201
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