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NASA NTRS2013

NIR Imaging Spectroscopy of the Inner Few Arcseconds of NGC 4151 with OSIRIS at Keck

We present H- and K-band data from the inner arcsecond of the Seyfert 1.5 galaxy NGC 4151 obtained with the adaptive optics assisted near-infrared imaging field spectrograph OSIRIS at the Keck Observatory. The angular resolution is about a few parsecs on-site and thus competes easily with optical images taken previously with the Hubble Space Telescope. We present the morphology and dynamics of most species detected but focus on the morphology and dynamics of the narrow line region (as traced by emission of [FeII]λ1.644 μm), the interplay between plasma ejected from the nucleus (as traced by 21 cm continuum radio data) and hot H2 gas and characterize the detected nuclear HeIλ2.058 μm absorption feature as a narrow absorption line (NAL) phenomenon. Emission from the narrow line region (NLR) as traced by [FeII] reveals a biconical morphology and we compare the measured dynamics in the [FeII] emission line with models proposing acceleration of gas in the NLR and simple ejection of gas into the NLR. In the inner 2.5 arcseconds the acceleration model reveals a better fit to our data than the ejection model.We also see evidence that the jet very locally enhances emission in [FeII] at certain positions in our field-of-view such that we were able to distinct the kinematics of these clouds from clouds generally accelerated in the NLR. Further, the radio jet is aligned with the bicone surface rather than the bicone axis such that we assume that the jet is not the dominant mechanism responsible for driving the kinematics of clouds in the NLR. The hot H2 gas is thermal with a temperature of about 1700 K. We observe a remarkable correlation between individual H2 clouds at systemic velocity with the 21 cm continuum radio jet. We propose that the radio jet is at least partially embedded in the galactic disk of NGC 4151 such that deviations from a linear radio structure are invoked by interactions of jet plasma with H2 clouds that are moving into the path of the jet because of rotation of the galactic disk of NGC 4151. Additionally, we observe a correlation of the jet as traced by the radio data, with gas as traced in Brγ and H2, at velocities between systemic and +/- 200 km/s at several locations along the path of the jet. The HeIλ2.058 μm line in NGC 4151 appears in emission with a blueshifted absorption component from an outflow. The emission (absorption) component has a velocity offset of 10 km/s (-280 km/s) with a Gaussian (Lorentzian) full-width (half-width) at half maximum of 160 km/s (440 km/s). The absorption component remains spatially unresolved and its kinematic measures differ from that of UV resonance absorption lines. From the amount of absorption we derive a lower limit of the HeI 2S column density of 1 × 10(exp 14) cm−2 with a covering factor along the line-of-sight of C(sub los) approximately equal to 0.1.

K-band data↗
NASA NTRS1989

The origin of the galactic emission in IRAS data

Using the high resolution IRAS data and the radial distribution of gaseous material and those of the interstellar radiation field (ISRF), a model of the Galactic infrared emission was built. The first step consisted of a separation of the diffuse emission in IRAS data from that of the well-defined strong Galactic sources. A well accepted idea is that IR emission comes from dust heated either by the ISRF and/or by internal cloud heating sources. Thus the IR galactic emission was modelled from radial distributions of gas and ISRF and the following three main hypothesis: (1) the dust-to-gas ration is the same in the whole Galaxy; (2) IR emission is proportional to local dust density; and (3) IR emission is also proportional to the local ISRF. The IR emission as modelled was integrated over each line of sight and compared with observed IRAS data. The results show that the IR diffuse component comes from dust associated with H1 and heated by the general ISRF. For the dust embedded in cold H2 component, the heating source is also the general ISRF while the warm component is explained by dust embedded in molecular clouds and heated by high-mass stars born in the close vicinity of the clouds and by disc population ISRF.

Caux, Emanuel↗
NASA NTRS2013

ERRATUM: FERMI Large Area Telescope Study of Cosmic-Rays and the Interstellar Medium in Nearby Molecular Clouds

In the published version of the paper, errors were made in calculating the exposure time due to an analysis mistake. While they do not affect gas emissivities of the R CrA and Cepheus & Polaris flare regions significantly (the differences are within the systematic uncertainty), that of the Chamaeleon region is increased by approx.20%. Although we claimed a difference of ∼50% in gas emissivity among these molecular cloud regions in the original paper, it is decreased to ∼30% (comparable to the sum of the statistical and systematic uncertainties) in the revised analysis. Therefore, our conclusion of the original paper, that a small variation (approx. 20%) of the CR density in the solar neighborhood exists, is not supported by the data if we take these uncertainties into account. On the other hand, the obtained XCO and XAv values, and the masses of gas calculated from them are not changed significantly (the differences are within the statistical errors). Errors and corrections in the original paper are summarized below. 1. In the Abstract (lines 5-6) and Section 3 (lines 4-5 in the 3rd paragraph) in the original paper, the gamma -ray emissivity above 250 MeV for the Chamaeleon region should be (7.2 +/- 0.1stat +/- 1.0sys) × 10(exp −27) photons/s/sr/H-atom, not (5.9 +/-0.1stat +0.9−1.0sys) × 10(exp −27) photons/s/sr/H-atom. 2. In the Abstract (lines 8-10), "Whereas the energy dependences of the emissivities agree well with that predicted from direct CR observations at the Earth, the measured emissivities from 250 MeV to 10 GeV indicate a variation of the CR density by approx.20% in the neighborhood of the solar system, even if we consider the systematic uncertainties." should be changed to "The energy dependences of the emissivities agree well with that predicted from direct CR observations at the Earth. Although the measured emissivities from 250 MeV to 10 GeV differ by approx.30% among these molecular cloud regions, the difference is not significant if we take the systematic uncertainty into account." 3. Table 1 and Figure 13, which show gas emissivities and spectra for the Chamaeleon region in the original paper, should be changed to the Table 1 and Figure 1 as shown below. 4. Figure 16, which compares Hi gas emissivities among several regions in the original paper, should be changed to Figure 2 as shown below. 5. The text from the line 13 to the last one in the first paragraph of Section 4.1, "The spectral shapes for the three regions..., indicating a difference of the CR density between the Chamaeleon and the others as shown in Figure 16." should be changed to the paragraph that follows. "The shaded area of each spectrum indicates the systematic uncertainty as described in Section 3. We note that the systematic uncertainty of the LAT effective area (5% at 100 MeV and 20% at 10 GeV; Rando et al. 2009) does not affect the relative value of emissivities. The effect of unresolved point sources is small; we have verified that the obtained emissivities are almost unaffected by decreasing the threshold for point sources from TS = 100 to TS = 50. We also confirmed that the residual excess of photons around (l = 280deg to 288deg, b = −20deg to −12deg; see the bottom panel of Figure 8) in the Chamaeleon region does not affect the local Hi emissivity very much. Thus the total systematic uncertainty is reasonably expressed by the shaded area shown in Fig. 1.

emissivities↗
NASA NTRS1994

Fundamental and harmonic radiation in type III solar radio bursts

Type III solar radio bursts are investigated by modeling the propagation of the electron beam and the generation and subsequent propagation of waves to the observer. Predictions from this model are compared in detail with particle, Langmuir wave, and radio data from the International Sun Earth Explorer-3 (ISSE-3) spacecraft and with other observations to clarify the roles of fundamental and harmonic emission in type III radio bursts. Langmuir waves are seen only after the arrival of the beam, in accord with the standard theory. These waves persist after a positive beam slope is last resolved, implying that sporadic positive slopes persist for some time, unresolved but in accord with the predictions of stochastic growth theory. Local electromagnetic emission sets in only after Langmuir waves are seen, in accord with the standard theory, which relies on nonlinear processes involving Langmuir waves. In the events investigated here, fundamental radiation appears to dominate early in the event, followed and/or accompanied by harmonic radiation after the peak, with a long-lived tail of multiply scattered fundamental or harmonic emission extending long afterwards. These results are largely independent of, but generally consistent with, the conclusions of earlier works.

Robinson, P. A.↗
NASA NTRS1984

Limits on soft X-ray flux from distant emission regions

The all-sky soft X-ray data of McCammon et al. and the new N sub H survey (Stark et al. was used to place limits on the amount of the soft X-ray diffuse background that can originate beyond the neutral gas of the galactic disk. The X-ray data for two regions of the sky near the galactic poles are shown to be uncorrelated with 21 cm column densities. Most of the observed x-ray flux must therefore originate on the near side of the most distant neutral gas. The results from these regions are consistent with X-ray emission from a locally isotropic, unabsorbed source, but require large variations in the emission of the local region over large angular scales.

Burrows, D. N.↗
NASA NTRS1984

Limits on soft X-ray flux from distant emission regions

The all-sky soft X-ray data of McCammon et al., and the new N sub H survey (Stark et al.) was used to place limits on the amount of the soft X-ray diffuse background that can originate beyond the neutral gas of the galactic disk. The X-ray data for two regions of the sky near the galactic poles are shown to be uncorrelated with 21 cm column densities. Most of the observed X-ray flux must therefore originate on the near side of the most distant neutral gas. The results from these regions are consistent with X-ray emission from a locally isotropic, unabsorbed source, but require large variations in the emission of the local region over large angular scales.

Burrows, D. N.↗
NASA NTRS1983

Radio blips and hard X-rays in solar flares

The properties of short, narrow-band spikes occurring in groups at decimetric wavelengths have been extensively analyzed. The bursts, termed blips in the literature, have been found to appear in the impulsive phase of flares. They are associated with hard X-ray emission in 40 percent of all cases with simultaneous coverage. The correspondence between blips and X-ray spikes is generally not one-to-one, blips being more numerous than X-ray spikes. In some cases, however, close correlations between single events have been found. Blips have been discovered to drift in frequency and to decay in time similarly to type III bursts at lower frequency. They also resemble type III bursts in polarization. An analysis of starting frequencies, however, clearly shows that blips and type III bursts belong to different statistical populations. The narrow bandwidth of blips, the major qualitative difference with respect to type III bursts, suggests that blips are the signature of electron beams which either decay rapidly or have a locally enhanced emission due to the presence of some low-frequency wave. Blips have been shown to be an impulsive phase phenomenon occurring at densities of one to three billion per cu cm in the low corona.

Benz, A. O.↗
NASA NTRS1994

An X-ray and optical study of the supernova remnant W44

We report the results of a 8000 s observation of the supernova remnant W44 using the ROSAT Position Sensitive Proportional Counter (PSPC). The image shows the same centrally peaked morphology observed by the Einstein IPC and contrasts with the shell-like radio morphology. The eastern limb shows a lack of X-ray emission within the radio shell, probably due to the interaction between the Supernova Remnants (SNR) and a molecular cloud. No counterpart to the pulsar 1853 + 01 in W44 has been detected, with L(sub X) less than 1.3 x 10(exp 32) ergs/s in the 0.2 to 2.4 keV band. The spectral analysis of the central part of W44, combining EXOSAT ME and Einstein SSS data, shows that the shocked plasma has not reached ionization equilibrium. The best nonequilibrium fit to PSPC, ME, and SSS spectra gives Eta = 10(exp 51) ergs cm(exp -6), T(sub s) = 10(exp 7) K with T(sub e) = T(sub i), suggesting conditions are approaching ionization equilibrium. There is no evidence of enhanced abundances of Mg, Si, S, or Fe. The variation of temperature and column density was obtained region by region using the PSPC and Einstein IPC. The temperature is largely uniform over the remnant, but strong column density variations are found to be consistent with molecular clouds in the line of sight. An evaporation model with a two-phase interstellar medium structure of clumps and interclump gas (White & Long 1991) can explain the X-ray centrally peaked morphology of W44. The clumps remaining behind a SN shock provide a reservoir of material, and evaporat e to increase the density of X-ray emitting gas in the interior of a SNR. The uniform temperature distribution of W44 strongly supports the predictions of this model. In addition, mosaiced H alpha and (S II) images of W44, taken using the prime focus universal extragalactic instrument (PFUEI) camera on the Palomar 60 sec telescope, reveal the first discovery of optical filaments (both H alpha and (S II)) in the northwestern and southeastern portion of the remnant, within the X-ray emitting region. The optical filaments and the X-ray image showing locally brighter emission and clumps along the filaments suggest both are produced by the interaction between the supernova shock front and regions of enhanced ambient density.

Rho, Jeongee↗
NASA NTRS1972

Measurements of O(1 D) quenching rates in the F-region

In-situ determinations of the quenching of O(1 D) atoms by N2 and O2 molecules were made from observations of 6300 A nightglow intensity enhancements produced by the Platteville 1.6 MW transmitter. The heating of F-region electrons near the point of reflection of the RF wave leads to electron impact excitation of oxygen atoms to the O(1 D) state. It is shown that the resulting region of enhance 6300 A emission is localized to the region of electron energy absorption for heating at the lower altitudes. At 225 km the measured time constants for intensity buildup following transmitter turn-on and for intensity decay following turn-off are identical and equal to (13 plus or minus 1) sec. Time constants varying from 30 to 80 sec are found for the altitude range 260 to 300 km. The inferred quenching coefficient for the whole altitude range, 225 to 300 km, is 4.4 + 2 or - 1 x 10 to the minus 11th power cu cm/sec at 950 K, in good agreement with laboratory data. The quenching frequency obtained at 225 km, when referred to the altitude 120 km, is equal to (21 plus or minus 2)/sec, in agreement with less direct ionospheric determinations.

Sipler, D. P.↗
NASA NTRS1975

Sensitivity limits of an infrared heterodyne spectrometer for astrophysical applications

A discussion and an evaluation of the degradation in sensitivity is given for a heterodyne spectrometer employing a HgCdTe photodiode mixer and tunable diode lasers. The minimum detectable source brightness is considered as a function of the mixer parameters, transmission coefficient of the beam splitter, and local oscillator emission powers. The degradation in the minimum detectable line source brightness which results from the bandwidth being a function of the line width is evaluated and plotted as a function of the wavelength and bandwidth for various temperature to mass ratios. It is shown that the minimum achievable degradation in the sensitivity of a practical astronomical heterodyne spectrometer is approximately 30. Estimates of signal-to-noise ratios with which infrared line emission from astronomical sources of interest may be detected are given.

Abbas, M. M.↗
NASA NTRS1976

Intense soft X-ray flux from Her-1

An intense flux of soft X-rays extending up to at least 1 keV has been observed from Her X-1. If the soft X-ray intensity is corrected for interstellar absorption the luminosity between 0.16 and 1 keV is comparable to that from 2-10 keV. The soft X-rays are modulated with the 1.24 sec period observed at higher energies but are approximately 180 deg out of phase with the high energy flux. These results extend the detection of this flux to higher energy, a different binary phase, and to a time 19 periods (of the 35 day cycle) later. These observations suggest that this soft emission is a stable feature in the spectrum of this source during its X-ray on state and that this emission is local to Her X-1.

Catura, R. C.↗
NASA NTRS1976

Sensitivity limits of an infrared heterodyne spectrometer for astrophysical applications

A discussion and an evaluation of the degradation in sensitivity are given for a heterodyne spectrometer employing a HgCdTe photodiode mixer and tunable diode lasers. The minimum detectable source brightness is considered as a function of the mixer parameters, transmission coefficient of the beam splitter, and local oscillator emission powers. The degradation in the minimum detectable line source brightness that results from the bandwidth being a fraction of the line width is evaluated and plotted as a function of the wavelength and bandwidth for various temperature to mass ratios. It is shown that the minimum achievable degradation in the sensitivity of a practical astronomical heterodyne spectrometer is about 30. Estimates of SNRs with which IR line emission from astronomical sources of interest may be detected are given.

Abbas, M. M.↗
NASA NTRS1977

The local time variation of ELF emissions during periods of substorm activity

A statistical study is reported concerning the occurrence probability of ELF emissions observed on the low-altitude polar-orbiting satellite OGO 6 during periods of substorm activity. Over 160 individual substorm periods have been selected and analyzed during the period from June 1969 to October 1970. The statistical results are discussed, taking into account ELF response to substorm activity and emissions during the recovery phase of magnetic storms.

Thorne, R. M.↗
NASA NTRS1981

Observations of the wavelength dependence of the average contrast of sunspots

The Extreme Limb Photometer has been used to observe the contrast of sunspots and faculae in conjunction with the Active Cavity Radiometer Irradiance Monitor on the SMM spacecraft. Some of these observations were obtained at five wavelengths from 0.43 to 1.01 micron. The largest average contrast at 0.52 micron was -17% over an area 38.5 x 51 in covering only the largest spot in Boulder AR no. 2684. It was found, for five sunspots, far from the limb, that the wavelength dependence of the contrast, averaged over the entire sunspot, followed a 1/lambda-law. No evidence was found for localized bright emission around the sunspots with an upper limit of about 3%, a limit set by the granular intensity rms variation of 1.3% at 0.52 micron.

Chapman, G. A.↗
NASA NTRS1985

Initial phase of chromospheric evaporation in a solar flare

Attention is given to the initial phase of chromospheric evaporation in the solar flare observed by the Solar Maximum Mission's Hard X-ray Imaging Spectrometer, on May 21, 1980. Images of the flaring region in the 3.5-8.0 and 16-30 keV energy bands indicate that both the soft and hard X-ray emissions are localized near the footpoints early in the event, while they are weaker from the rest of the flaring loop system; this implies that there is no heating taking place at the top of the loops, while energy is primarily deposited at their base. Observations of the energy deposition in the chromosphere by electrons accelerated in the flare region to energies above 25 keV furnish further support for an interpretation of plasma upflows as the mechanism responsible for the formation of the soft X-ray flare, identified with chromospheric evaporation.

Antonucci, E.↗
NASA NTRS1986

Comprehensive analysis of Shuttle Orbiter leeside surface infrared imagery obtained during atmospheric entry

The thermographic analysis techniques developed for processing of data from the Shuttle Infrared Leeside Temperature Sensing (SILTS) experiment are discussed. The SILTS experiment will obtain high-spatial-resolution infrared images of the leeside of the Space Shuttle Orbiter during atmospheric entry by means of a scanning infrared radiometer located atop the orbiter's vertical stabilizer. Comprehensive analysis of the SILTS thermography requires accurate consideration of all those factors (such as geometry of the observed surfaces, local surface emissivity, solar radiation, and other potential sources of image degradation) which may potentially affect the output of the infrared radiometer. An overview of the entire data processing procedure and brief descriptions of the data processing algorithms are presented.

Myrick, D. L.↗