Far-ultraviolet Emission-line Morphologies of the Supernova Remnant G65.3+5.7

We present the first far-ultraviolet (FUV) emission-line morphologies of the whole region of the supernova remnant (SNR) G65.3+5.7 using the FIMS/SPEAR data. The morphologies of the C IV {\lambda}{\lambda}1548, 1551, He II {\lambda}1640, and O III] {\lambda}{\lambda}1661, 1666 lines appear to be closely related to the optical and/or soft X-ray images obtained in previous studies. Dramatic differences between the C IV morphology and the optical [O III] {\lambda}5007 image provide clues to a large resonant-scattering region and a foreground dust cloud. The FUV morphologies also reveal the overall distribution of various shocks in different evolutionary phases and an evolutionary asymmetry between the east and the southwest sides in terms of Galactic coordinates, possibly due to a Galactic density gradient in the global scale. The relative X-ray luminosity of G65.3+5.7 to C IV luminosity is considerably lower than those of the Cygnus Loop and the Vela SNRs. This implies that G65.3+5.7 has almost evolved into the radiative stage in the global sense and supports the previous proposal that G65.3+5.7 has lost its bright X-ray shell and become a member of mixed-morphology SNRs as it has evolved beyond the adiabatic stage.Comment: 6 pages, 3 figures, accepted for publication in The Ap

The role of the intergeniculate leaflet in the circadian response to light

Mammalian circadian rhythms are generated and regulated by a pacemaker located in the suprachiasmatic nucleus (SCN) in the hypothalamus. Transmission of photic information to the SCN occurs via a direct projection from the retina, the retinohypothalamic tract, and an indirect projection from the retinorecipient intergeniculate leaflet (IGL), the geniculohypothalamic tract. The retinohypothalamic tract is necessary for synchronization of rhythms to environmental light-dark cycles. In contrast, although the IGL is strategically located to convey light information to the SCN, a role for the IGL in photic entrainment has not been established. IGL-lesioned hamsters have been shown to entrain normally to light-dark cycles; effects of the lesion have been manifested in slower rates of re-entrainment to shifts in the light-dark cycle and small changes in the size of light-induced phase shifts. In the present thesis, the relationship between the IGL and the circadian response to light is explored in two sets of experiments. The first three experiments evaluated activation of IGL neurons by light using immunohistochemical expression of Fos protein as a marker of cellular activation. In rodents, light-induced Fos in SCN neurons is phase dependent and is correlated with the effectiveness of such light to phase shift circadian rhythms. Furthermore, because the IGL has been implicated in the effects of nonphotic stimuli on circadian rhythms, the induction of Fos in the SCN and IGL in response to nonphotic manipulations was assessed. Results demonstrate that, in contrast to light-induced Fos in the SCN, light induces Fos protein in the IGL regardless of circadian time, and continues to do so as long as the animal is exposed to light. Moreover, nonphotic manipulations induce Fos in both SCN and IGL. However, in the IGL, Fos expression in response to such treatments was enhanced during the light phase of the light-dark cycle. Pharmacological manipulations that attenuate both light-induced phase shift and Fos expression in the SCN are without effect on light-induced Fos expression in the IGL. The effects of electrolytic lesions of the IGL on circadian temperature rhythms were examined under different lighting schedules in the final two experiments using a telemetry system. Rhythms in these animals were compared to those of intact controls as well as to rhythms of rats with neurotoxic damage to the visual system resulting from neonatal monosodium. glutamate (MSG) treatment. IGL-lesioned rats entrained normally to light-dark cycles consisting of 12 hours of light followed by 12 hours of darkness, and showed the disruption of rhythmicity after prolonged constant light housing seen in intact animals. However, in contrast to intact and MSG-treated rats, IGL-lesioned animals exhibited free-running temperature rhythms under a skeleton photoperiod consisting of one-hour of light exposure at times corresponding to dusk and dawn. Because nocturnal animals normally experience light only around dusk and dawn, the inability to entrain to this ecologically relevant lighting schedule suggests that the IGL plays a critical role in photic entrainment

Dramatic robustness of a multiple delay dispersed interferometer to spectrograph errors: how mixing delays reduces or cancels wavelength drift

We describe demonstrations of remarkable robustness to instrumental noises by using a multiple delay externally dispersed interferometer (EDI) on stellar observations at the Hale telescope. Previous observatory EDI demonstrations used a single delay. The EDI (also called “TEDI”) boosted the 2,700 resolution of the native TripleSpec NIR spectrograph (950-2450 nm) by as much as 10x to 27,000, using 7 overlapping delays up to 3 cm. We observed superb rejection of fixed pattern noises due to bad pixels, since the fringing signal responds only to changes in multiple exposures synchronous to the applied delay dithering. Remarkably, we observed a ~20x reduction of reaction in the output spectrum to PSF shifts of the native spectrograph along the dispersion direction, using our standard processing. This allowed high resolution observations under conditions of severe and irregular PSF drift otherwise not possible without the interferometer. Furthermore, we recently discovered an improved method of weighting and mixing data between pairs of delays that can theoretically further reduce the net reaction to PSF drift to zero. We demonstrate a 350x reduction in reaction to a native PSF shift using a simple simulation. This technique could similarly reduce radial velocity noise for future EDI’s that use two delays overlapped in delay space (or a single delay overlapping the native peak). Finally, we show an extremely high dynamic range EDI measurement of our ThAr lamp compared to a literature ThAr spectrum, observing weak features (~0.001x height of nearest strong line) that occur between the major lines. Because of individuality of each reference lamp, accurate knowledge of its spectrum between the (unfortunately) sparse major lines is important for precision radial velocimetry

Observation of the Far-ultraviolet Continuum Background with SPEAR/FIMS

We present the general properties of the far-ultraviolet (FUV; 1370-1720A) continuum background over most of the sky, obtained with the Spectroscopy of Plasma Evolution from Astrophysical Radiation instrument (SPEAR, also known as FIMS), flown aboard the STSAT-1 satellite mission. We find that the diffuse FUV continuum intensity is well correlated with N_{HI}, 100 $\mu$m, and H-alpha intensities but anti-correlated with soft X-ray. The correlation of the diffuse background with the direct stellar flux is weaker than the correlation with other parameters. The continuum spectra are relatively flat. However, a weak softening of the FUV spectra toward some sight lines, mostly at high Galactic latitudes, is found not only in direct-stellar but also in diffuse background spectra. The diffuse background is relatively softer that the direct stellar spectrum. We also find that the diffuse FUV background averaged over the sky has about the same level as the direct-stellar radiation field in the statistical sense and a bit softer spectrum compared to direct stellar radiation. A map of the ratio of 1400-1510A to 1560-1660A shows that the sky is divided into roughly two parts. However, this map shows a lot of patchy structures on small scales. The spatial variation of the hardness ratio seems to be largely determined by the longitudinal distribution of spectral types of stars in the Galactic plane. A correlation of the hardness ratio with the FUV intensity at high intensities is found but an anti-correlation at low intensities. We also find evidence that the FUV intensity distribution is log-normal in nature.Comment: 39 pages, 26 figures, accepted for publication in ApJ

Far-Ultraviolet Cooling Features of the Antlia Supernova Remnant

We present far-ultraviolet observations of the Antlia supernova remnant obtained with Far-ultraviolet IMaging Spectrograph (FIMS, also called SPEAR). The strongest lines observed are C IV 1548,1551 and C III 977. The C IV emission of this mixed-morphology supernova remnant shows a clumpy distribution, and the line intensity is nearly constant with radius. The C III 977 line, though too weak to be mapped over the whole remnant, is shown to vary radially. The line intensity peaks at about half the radius, and drops at the edge of the remnant. Both the clumpy distribution of C IV and the rise in the C IV to C III ratio towards the edge suggest that central emission is from evaporating cloudlets rather than thermal conduction in a more uniform, dense medium.Comment: 9 pages, 4 figures, will be published in ApJ December 1, 2007, v670n2 issue. see http://astro.snu.ac.kr/~jhshinn/ms.pd

Gravitating Self-dual Chern-Simons Solitons

Self-dual solitons of Chern-Simons Higgs theory are examined in curved spacetime. We derive duality transformation of the Einstein Chern-Simons Higgs theory within path integral formalism and study various aspects of dual formulation including derivation of Bogomolnyi type bound. We find all possible rotationally-symmetric soliton configurations carrying magnetic flux and angular momentum when underlying spatial manifolds of these objects comprise a cone, a cylinder, and a two sphere.Comment: 38 pages, 8 figures (Pslatex files are included in the text.) Two references are added. To appear in Annals of Physic