27 research outputs found
Multipolar Planetary Nebulae: Not as Geometrically Diversified as Thought
Planetary nebulae (PNe) have diverse morphological shapes, including
point-symmetric and multipolar structures. Many PNe also have complicated
internal structures such as torus, lobes, knots, and ansae. A complete
accounting of all the morphological structures through physical models is
difficult. A first step toward such an understanding is to derive the true
three-dimensional structure of the nebulae. In this paper, we show that a
multipolar nebula with three pairs of lobes can explain many of such features,
if orientation and sensitivity effects are taken into account. Using only six
parameters - the inclination and position angles of each pair - we are able to
simulate the observed images of 20 PNe with complex structures. We suggest that
the multipolar structure is an intrinsic structure of PNe and the statistics of
multipolar PNe has been severely underestimated in the past.Comment: 36 pages, 5 figures, 2 table
Extremely Strong ^{13}CO J=3-2 Line in the "Water Fountain" IRAS 16342-3814: Evidence for the Hot-Bottom Burning
We observed four "water fountain" sources in the CO J=3-2 line emission with
the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope in
2010-2011. The water fountain sources are evolved stars that form high-velocity
collimated jets traced by water maser emission. The CO line was detected only
from IRAS 16342-3814. The present work confirmed that the ^{12}CO to ^{13}CO
line intensity ratio is ~1.5 at the systemic velocity. We discuss the origins
of the very low ^{12}CO to ^{13}CO intensity ratio, as possible evidence for
the "hot-bottom burning" in an oxygen-rich star, and the CO intensity variation
in IRAS 16342-3814.Comment: 10 pages, 3 figures, accepted for publication to the Publications of
the Astronomical Society of Japan, Vol. 64, No.
Pilot VLBI Survey of SiO v=3 J=1--0 Maser Emission around Evolved Stars
In this Letter, we report detections of SiO v=3 J=1--0 maser emission in very
long baseline interferometric (VLBI) observations towards 4 out of 12
long-period variable stars: WX Psc, R Leo, W Hya, and T Cep. The detections
towards WX Psc and T Cep are new ones. We also present successful astrometric
observations of SiO v=2 and v=3 J=1--0 maser emissions associated with two
stars: WX Psc and W Hya and their position-reference continuum sources:
J010746.0+131205 and J135146.8-291218 with the VLBI Exploration of Radio
Astrometry (VERA). The relative coordinates of the position-reference continuum
source and SiO v=3 maser spots were measured with respect to those of an SiO
v=2 maser spot adopted as fringe-phase reference. Thus the faint continuum
sources were inversely phase-referenced to the bright maser sources. It implies
possible registration of multiple SiO maser line maps onto a common coordinate
system with 10 microarcsecond-level accuracy.Comment: 5 Pages, 3 figures, Fig.3 and Tab. 2 were corrected; Publications of
the Astronomical Society of Japan, Vol. 64, No. 6 issued on 2012 December 2
Robust estimation of bacterial cell count from optical density
Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data
Three dimensional morphology of the dumbbell nebula and the ring nebula
published_or_final_versionPhysicsMasterMaster of Philosoph
Extremely Strong 13CO J = 3→2 Line in the "Water Fountain" IRAS 16342-3814: Evidence for the Hot-Bottom Burning
We observed four "water fountain" sources in the CO J = 3→2 line emission with the Atacama Submillimeter Telescope Experiment (ASTE) 10m telescope in 2010–2011. The water fountain sources are evolved stars that form high-velocity collimated jets traced by H2O maser emission. The CO line was detected only from IRAS 16342-3814. The present work confirmed that the 12CO to 13CO line intensity ratio is ~1.5 at the systemic velocity. We discuss the origins of the very low 12CO-to-13CO intensity ratio, as possible evidence for "hot-bottom burning" in an oxygen-rich star, and the CO intensity variation in IRAS 16342-3814