490 research outputs found
Extragalactic infrared spectroscopy
The spectra of galaxies in the near infrared atmospheric transmission windows are explored. Emission lines were detected due to molecular hydrogen, atomic hydrogen recombination lines, a line attributed to FEII, and a broad CO absorption feature. Lines due to H2 and FEII are especially strong in interacting and merging galaxies, but they were also detected in Seyferts and normal spirals. These lines appear to be shock excited. Multi-aperture measurements show that they emanate from regions as large as 15 kpc. It is argued that starbursts provide the most plausible and consistent model for the excitation of these lines, but the changes of relative line intensity of various species with aperture suggest that other excitation mechanisms are also operating in the outer regions of these galaxies
Expression of pheromone binding proteins during antennal development in the gypsy moth Lymantria dispar
We have identified 2 olfactory specific proteins in the gypsy moth Lymantria dispar that are uniquely associated with the male antennae, the principal olfactory organs of this animal. These proteins were the major soluble protein components of the olfactory sensilla, present in equivalent amounts. Both proteins comigrated on SDS-PAGE, showing an apparent molecular mass of 15,000 Da but migrated separately on non-SDS-PAGE, indicating differences in net charge. N-terminal amino acid sequence analysis showed that the 2 proteins share 50% identity, indicating that they are genetically distinct homologs. Both proteins bound the L. dispar sexpheromone, associated with antisera prepared against the previously identified phermone-binding protein (PBP) of the moth Antheraea polyphemus, and shared sequence identity with the A. polyphemus PBP. These 2 proteins are therefore identified as L. dispar PBPs and are termed PBP1 and PBP2 based on their migration differences on non-SDS-PAGE. It is estimated that PBP1 and PBP2 are present in the sensilla lumen at a combined concentration of 13.4 mM. The expression of the L. dispar PBPs was examined during the 11 d development of the adult antenna. PBP1 and PBP2 were first detected by non-SDS-PAGE analysis and Coomassie blue staining 3 d before adult eclosion, on day A-3. Levels increased, reaching a plateau on day A-1 that continued into adult life. In vivo labeling studies indicated that the rate of PBP synthesis increased from A-3 to a plateau on A-2, where it remained into adult life. In vitro translations of antennal mRNAs indicated that translatable PBP mRNA was available at a very low level on day A-4, increased slightly on A-3 and dramatically on A-2, and remained at a high level into adult life. PBP mRNA represented the major translatable mRNA in the antenna during this period. It was estimated that the PBPs undergo a combined steady-state turnover of 8 x 10(7) molecules/hr/sensillum. Cursory in vivo and in vitro translation studies of antennal mRNA from A. polyphemus and Manduca sexta showed similar temporal patterns of PBP expression, suggesting that the L. dispar observations are general
Early Chandra X-ray Observations of Eta Carinae
Sub-arcsecond resolution Chandra observations of Eta Carinae reveal a 40
arcsec X 70 arcsec ring or partial shell of X-ray emission surrounding an
unresolved, bright, central source. The spectrum of the central source is
strongly absorbed and can be fit with a high-temperature thermal continuum and
emission lines. The surrounding shell is well outside the optical/IR bipolar
nebula and is coincident with the Outer Shell of Eta Carinae. The X-ray
spectrum of the Shell is much softer than that of the central source. The X-ray
Shell is irregular and only correlates well with optical features where a
bright X-ray knot coincides with a bright feature of the Outer Shell.
Implications for the binary model of the central source are discussed.Comment: 6 pages, 6 figures, accepted by Ap
A Multiwavelength Study of the Extreme AGN J2310-437
We present new X-ray, radio, and optical data for the unusual galaxy/cluster
system J2310-437. Our results confirm the presence of an active nucleus, and
suggest an interpretation as an anomalous BL Lac object of bulk relativistic
Doppler factor < 2, with an optically deficient radio-to-X-ray spectrum. The
radio, optical, and soft X-ray flux densities could lie along a single
power-law function, lacking the curvature typical of BL Lac objects. Compared
with other known sources that may have comparable multifrequency spectra,
J2310-437 is the most extreme. Its low isotropic optical/UV radiation is
consistent with the intensity of external photons governing the electron
spectral break through Compton cooling; in this source the external photon
density would be too low to produce a spectral break below the X-ray.Comment: 19 pages, including 10 figures, using emulateapj.sty and
apjfonts.sty. To appear in the Ap
Physical Properties of the X-ray Luminous SN 1978K in NGC 1313 from Multiwavelength Observations
We update the light curves from the X-ray, optical, and radio bandpasses
which we have assembled over the past decade, and present two observations in
the ultraviolet using the Hubble Space Telescope Faint Object Spectrograph. The
HRI X-ray light curve is constant within the errors over the entire observation
period. This behavior is confirmed in the ASCA GIS data obtained in 1993 and
1995. In the ultraviolet, we detected Ly-alpha, the [Ne IV] 2422/2424 A
doublet, the Mg II doublet at 2800 A, and a line at ~3190 A we attribute to He
I 3187. Only the Mg II and He I lines are detected at SN1978K's position. The
optical light curve is formally constant within the errors, although a slight
upward trend may be present. The radio light curve continues its steep decline.
The longer time span of our radio observations compared to previous studies
shows that SN1978K is in the same class of highly X-ray and radio-luminous
supernovae as SN1986J and SN1988Z. The [Ne IV] emission is spatially distant
from the location of SN1978K and originates in the pre-shocked matter. The Mg
II doublet flux ratio implies the quantity of line optical depth times density
of ~10^14 cm^-3 for its emission region. The emission site must lie in the
shocked gas.Comment: 32 pages, 13 figs; LaTeX with AASTEXv5; paper accepted, scheduled for
AJ, Dec 199
Superiority of deformable image co-registration in the integration of diagnostic positron emission tomography-computed tomography to the radiotherapy treatment planning pathway for oesophageal carcinoma
Aims
To investigate the use of image co-registration in incorporating diagnostic positron emission tomography-computed tomography (PET-CT) directly into the radiotherapy treatment planning pathway, and to describe the pattern of local recurrence relative to the PET-avid volume.
Materials and methods
Fourteen patients were retrospectively identified, six of whom had local recurrence. The accuracy of deformable image registration (DIR) and rigid registration of the diagnostic PET-CT and recurrence CT, to the planning CT, were quantitatively assessed by comparing co-registration of oesophagus, trachea and aorta contours. DIR was used to examine the correlation between PET-avid volumes, dosimetry and site of recurrence.
Results
Positional metrics including the dice similarity coefficient (DSC) and conformity index (CI), showed DIR to be superior to rigid registration in the co-registration of diagnostic and recurrence imaging to the planning CT. For diagnostic PET-CT, DIR was superior to rigid registration in the transfer of oesophagus (DSC = 0.75 versus 0.65, P < 0.009 and CI = 0.59 versus 0.48, P < 0.003), trachea (DSC = 0.88 versus 0.65, P < 0.004 and CI = 0.78 versus 0.51, P < 0.0001) and aorta structures (DSC = 0.93 versus 0.86, P < 0.006 and CI = 0.86 versus 0.76, P < 0.006). For recurrence imaging, DIR was superior to rigid registration in the transfer of trachea (DSC = 0.91 versus 0.66, P < 0.03 and CI = 0.83 versus 0.51, P < 0.02) and oesophagus structures (DSC = 0.74 versus 0.51, P < 0.004 and CI = 0.61 versus 0.37, P < 0.006) with a non-significant trend for the aorta (DSC = 0.91 versus 0.75, P < 0.08 and CI = 0.83 versus 0.63, P < 0.06) structure. A mean inclusivity index of 0.93 (range 0.79–1) showed that the relapse volume was within the planning target volume (PTVPET-CT); all relapses occurred within the high dose region.
Conclusion
DIR is superior to rigid registration in the co-registration of PET-CT and recurrence CT to the planning CT, and can be considered in the direct integration of PET-CT to the treatment planning process. Local recurrences occur within the PTVPET-CT, suggesting that this is a suitable target for dose-escalation strategies
Probing the X-Ray Binary Populations of the Ring Galaxy NGC 1291
We present Chandra studies of the X-ray binary (XRB) populations in the bulge
and ring regions of the ring galaxy NGC 1291. We detect 169 X-ray point sources
in the galaxy, 75 in the bulge and 71 in the ring, utilizing the four available
Chandra observations totaling an effective exposure of 179 ks. We report
photometric properties of these sources in a point-source catalog. There are
~40% of the bulge sources and ~25% of the ring sources showing >3\sigma
long-term variability in their X-ray count rate. The X-ray colors suggest that
a significant fraction of the bulge (~75%) and ring (~65%) sources are likely
low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate
that it is a low-luminosity AGN with moderate obscuration; spectral variability
is observed between individual observations. We construct 0.3-8.0 keV X-ray
luminosity functions (XLFs) for the bulge and ring XRB populations, taking into
account the detection incompleteness and background AGN contamination. We reach
90% completeness limits of ~1.5\times10^{37} and ~2.2\times10^{37} erg/s for
the bulge and ring populations, respectively. Both XLFs can be fit with a
broken power-law model, and the shapes are consistent with those expected for
populations dominated by LMXBs. We perform detailed population synthesis
modeling of the XRB populations in NGC 1291, which suggests that the observed
combined XLF is dominated by an old LMXB population. We compare the bulge and
ring XRB populations, and argue that the ring XRBs are associated with a
younger stellar population than the bulge sources, based on the relative
overdensity of X-ray sources in the ring, the generally harder X-ray color of
the ring sources, the overabundance of luminous sources in the combined XLF,
and the flatter shape of the ring XLF.Comment: 15 pages, 11 figures. Accepted for publication in Ap
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