Gaps in the emission line redshift distribution of QSOs

A gap in a distribution is the interval between two consecutive values. Gaps in the emission line redshift distribution of QSOs are analysed using up-to-date data comprising 371 objects. It is found that the distribution of gaps is not random, but follows a definite trend, depending on the mean value of the redshift in the region.     

A trend in the gaps in redshift distribution of QSOs

Analysis of gaps in the emission line redshift distribution of 537 QSOs shows a single definite trend in the distribution of the gaps. The trend is similar for radio-quiet objects, radio sources and all QSO's taken together. However, the trend does not suggest any periodicity in redshifts in any of the three cases.     

Distribution of gaps in emission line redshifts of QSOs

A gap in the distribution of a parameter is simply the absence of the parameter for the values corresponding to the gap. The gap in the emission line redshift (z) of QSOs thus represents absence of QSOs with emission line redshift values corresponding to the gap region. Gaps in emission line redshifts of QSOs have been analysed statistically with updated data consisting of 1549 values. The study indicates: (i) There is a critical redshiftz _c =2.4, which separates two distinct phases in the creation of QSOs. Forz>z _c , the creation appears to have been a slow process. Atz?z _c there was a triggering action which produced a burst of QSOs simultaneously. Forz _c , the rate of production of QSOs have been fast. (ii) The distribution of gaps atz _c ; appear to be consequence of periodicities, provided the periodicities involved are perfect and the redshift values are accurate. (iii) The distribution of gaps atz>z _c are not random, but follow a definite trend.     

Measurements of solar magnetic fields by Fourier transform techniques

The Fourier techniques of Paper I have been exhaustively calibrated using Unno's results for the absorption profile of a simple Zeeman triplet. If a simple transformation is applied to the normalized line depths, then magnetic field strengths and inclination angles can be measured very accurately from noisy, saturated line profiles. Systematic errors caused by saturation effects can be estimated and reduced by varying one parameter. When a significant fraction of the line profile is unsplit and unpolarized, large errors may be made in measurements of low fields, unless the line is sufficiently weak. For a weak line, a vertical field of 1600 gauss can be measured to 10% accuracy even when 70% of the line profile is stray light. These stray light errors are troublesome in measuring fields of gaps and pores but not sunspots. Numerical results of our error analysis are presented graphically.     

Interpretation of Localized Deficits in Coronal Emission

Coronal images recorded above the limb in Fexiv (530.3 nm) and Fex (637.5 nm) sometimes have localized regions of anomalously low emission, with the appearance of an abrupt gap in the background corona. These dark spaces have been previously described in the literature in the case of the 530.3 nm line and tentatively explained by reduced coronal plasma density and/or a decrease in the line intensity due to temperatures above or below the optimal ionization temperature for Fexiv. However, loops are sometimes observed spanning gaps, with diminished loop brightness over the region of the gap. It is concluded that at least some of these regions of reduced brightness are caused by absorption of the coronal emission. An analysis reveals that absorption by coronal ions is inadequate as a mechanism to explain the phenomenon. Absorption by neutral hydrogen is, however, consistent with the observations in terms of the reduced brightness of the gaps. The concentration of cool material in the coronal environment associated with large magnetic fields on the disk could explain the gaps. Hence, neutral hydrogen continuum absorption appears to provide a plausible interpretation of, at least, some coronal gaps. Based on this result and from measured intensities, the electron density in the region of a gap is derived and found to be consistent with estimates derived elsewhere.     

引力透镜类星体SDSS J1001+5027吸收线证认

基于斯隆数字化巡天(Sloan Digital Sky Survey,SDSS)第12期数据(data release 12,DR12)的光谱,分析引力透镜类星体SDSS J1001+5027的A, B两个像的光谱。两个像光谱的红移分别为1.84132±0.00024和1.84545±0.00012,透镜天体红移约为0.415。通过证认可靠的CⅣλλ1548, 1551或Mg Ⅱλλ2796, 2803窄吸收双线的方法,证认出A, B两个像的光谱中红移分别为1.60677±0.00012, 0.87140±0.00007和0.41455±0.00006的3个吸收系统。从3个吸收系统共证认出27条窄吸收线。测量27条窄吸收线的等值宽度,再通过分析、比较3个吸收系统在A, B两个像光谱中吸收线的数量及等值宽度的差异,给出了3个吸收系统在引力透镜类星体SDSS J1001+5027视线方向可能的分布示意图。     

类星体Lα森林吸收线密度与发射红移相关性的再考察

继文[1]之后,本文利用15个中—高红移类星体的Lα森林构成统计样本,再度考察了Lα森林吸收线密度N(Z_(abs))与发射红移Z_(em)的相关性。本文的统计样本包含的红移范围比文[1]更大:类星体的发射红移值从1.715到3.750,Lα森林吸收线红移范围从1.501到3.780;统计方法亦与文[1]略有差异。统计结果再度表明,Lα森林吸收线密度N(Z_(abs))明显依赖于类星体自身的发射红移Z_(em),这不仅在于Z_(em)越大的类星体其全部吸收线的平均数密度N(Z_(abs))也越大,更重要的是,对于相同的吸收红移值Z_(abs)而言,N(Z_(abs))在统计意义上明显地随Z_(em)的增大而增大。文末对所得的结果作了讨论。     

Gravitationally distorted P Cygni profiles from outflows near compact objects

We consider resonant absorption in a spectral line in the outflowing plasma within several tens of Schwarzschild radii from a compact object. We take into account both Doppler and gravitational shifting effects and reformulate the theory of P Cygni profiles in these new circumstances. It is found that a spectral line may have multiple absorption and emission components depending on how far the region of interaction is from the compact object and what the distribution of velocity and opacity is. Profiles of spectral lines produced near a neutron star or a black hole can be strongly distorted by Doppler blue- or redshifting and gravitational redshifting. These profiles may have both red- and blueshifted absorption troughs. The result should be contrasted with classical P Cygni profiles, which consist of redshifted emission and blueshifted absorption features.
We suggest that this property of line profiles to have complicated narrow absorption and emission components in the presence of strong gravity may help researchers to study spectroscopically the innermost parts of an outflow.     

The angle-dependent redistribution functionsR III andR IV: Line absorption probability distribution functions and reemission coefficients

The line absorption probability distribution functions and the reemission coefficients are derived for the non-coherent scattering functionsR _III andR _IV. The appropriate line profile function forR _III is shown to be a simple Voigt function, while forR _IV, the line absorption probability distribution function is more complex involving a linear combination of two Voigt functions and another more complex probability distribution. The structure of the reemission coefficients forR _III andR _IV is then discussed.     

Secular and orbital variability of Cir X-1 observed in optical spectra

We have observed variations in the optical emission lines from the X-ray binary Circinus X-1. These variations may be attributed both to orbital variations and to long term secular changes in line strength. We have detected double-peaked H α emission lines on two occasions, providing the first direct evidence for an accretion disc in the system. The separation of the peaks was different on the two occasions, suggesting that the disc might have a different size. The equivalent width of the emission lines dropped by more than a factor of three between 1999 and 2000; this continues the trend seen in earlier data, so that the H α equivalent width has now declined by a factor of 20 since 1976. The emission lines do not appear to show signature of orbital motion, except for the data taken near phase 0, which show a significant velocity shift.
We have observed an absorption component to the He  i lines on one occasion. We suggest that, unlike the P Cygni profiles seen in X-ray spectra, this absorption does not arise in the accelerating zone of a radiatively driven wind. Instead, the absorption arises in material previously ejected from the system. It was only seen on this one occasion because the strength of the emission line had dropped dramatically.     

The redshift distribution of quasar absorption lines and its origin

We have made statistical analyses of current data on the absorption line redshifts of quasars. All our results, including the distribution of relative velocities and the power-spectrum of the redshift distribution of absorption systems, are in favour of the cosmological hypothesis of the origin of the quasar absorption lines. We point out that the peaks in the relative velocity distribution are no compelling evidence for the rival, intrinsic hypothesis because they can be well explained by the model of density perturbation in the early universe [10].     

On the Molecular Line Absorption in the Li I Doublet 6708 Å Region for Evolved Star Atmospheres

Molecular line lists from latest molecular data bases have been analysed for the absorption in the Li I doublet line 6708 Å region. Their contribution to the line opacity has been estimated by the synthetic spectra method with Kurucz late model atmospheres for various temperatures and log g values.     

X-ray continuum slope and X-ray spectral features in NLS1 galaxies

The idea that some of the unusual features in the X-ray spectra of Narrow-Line Seyfert 1 galaxies (NLS1s) are due to the steep X-ray continuum is tested by comparing photoionization model calculations with various observed properties of Seyfert 1 galaxies. A meaningful comparison must involve the careful use of the “right” X-ray ionization parameter, designated here U(oxygen). When this is done, it is found that the strength of the continuum absorption features is insensitive to the exact slope of the 0.1–50 keV continuum. It is also shown that the complex of iron L-shell lines near 1 keV can produce strong absorption and emission features, depending on the gas distribution and line widths. While this may explain some unusual X-ray features in AGN, the predicted intensity of the features do not distinguish NLS1s from broader line sources. Finally, acceleration of highly ionized gas, by X-ray radiation pressure, is also not sensitive to the exact slope of the X-ray continuum.     

An Overview of the Disposition of Solar Radiation in the Lower Atmosphere: Connections to the SORCE Mission and Climate Change

Solar radiation is the primary energy source for many processes in Earth's environment and is responsible for driving the atmospheric and oceanic circulation. The integrated strength and spectral distribution of solar radiation is modified from the space-based {Solar {Radiation and {Climate (SORCE) measurements through scattering and absorption processes in the atmosphere and at the surface. Understanding how these processes perturb the distribution of radiative flux density is essential in determining the climate response to changes in concentration of various gases and aerosol particles from natural and anthropogenic sources, as is discerning their associated feedback mechanisms. The past decade has been witness to a tremendous effort to quantify the absorption of solar radiation by clouds and aerosol particles via airborne and space-based observations. Vastly improved measurement and modeling capabilities have enhanced our ability to quantify the radiative energy budget, yet gaps persist in our knowledge of some fundamental variables. This paper reviews some of the many advances in atmospheric solar radiative transfer as well as those areas where large uncertainties remain. The SORCE mission's primary contribution to the energy budget studies is the specification of the solar total and spectral irradiance at the top of the atmosphere.     

1983年日全食闪光谱中氦D3线的研究

我们对１９８３年日食闪光谱中的Ｄ３线进行了光度测量，加上比较可靠的定标系数，得到了氦Ｄ３线的绝对表面亮度分布，由此还求出了氦的密芳随高度的分布。其结果与以前观测结果大体一致。Ｇｕｌｙａｅｖ由统计发现，Ｄ３线的绝对亮度有着随太阳黑子数增加而下降这一趋势。我们的结果符合这一趋势。     

High-resolution Martian atmosphere modeling

A multilayer radiative transfer, high-spectral-resolution infrared model of the lower atmosphere of Mars has been constructed to assess the effect of scattering on line profiles. The model takes into account aerosol scattering and absorption and includes a line-by-line treatment of scattering and absorption by CO₂ and H₂O. The aerosol complex indices of refraction used were those measured on montmorillonite and basalt chosen on the basis of Mars ir data from the NASA Lear Airborne Observatory. The particle sizes and distribution were estimated using Viking data. The molecular line treatment employs the AFGL line parameters and Voigt profiles. The modling results indicate that the line profiles are only slightly affected by normal aerosol scattering and absorption, but the effect could be appreciable for heavy loading. The technique described permits a quantitative approach to assessing and correcting for the effect of aerosols on lineshapes in planetary atmospheres.     

Laser radiation in active amplifying media treated as a transport problem: Transfer equation derived and exactly solved

The flow of laser radiation in a plane-parallel cylindrical slab of active amplifying medium with axial symmetry is treated as a problem in radiative transfer. The appropriate one-dimensional transfer equation describing the transfer of laser radiation has been derived by an appeal to Einstein'sA, B coefficients (describing the processes of stimulated line absorption, spontaneous line emission, and stimulated line emission sustained by population inversion in the medium) and considering the rate equations to completely establish the rational of the transfer equation obtained. The equation is then exactly solved and the angular distribution of the emergent laser beam intensity is obtained; its numerically computed values are given in tables and plotted in graphs showing the nature of peaks of the emerging laser beam intensity about the axis of the laser cylinder.     

Some trends in the red-shift distribution of quasi-stellar objects and related peculiar galaxies

Gaps in the red-shift distribution of quasi-stellar objects and related peculiar galaxies have been studied using 205 sources. The result indicates certain definite trends in the distribution of the gaps but does not suggest any periodicity when the entire sample is considered.     

Neutron absorption constraints on the composition of 4 Vesta

Global maps of the macroscopic thermal neutron absorption cross section of Vesta's regolith by the Gamma Ray and Neutron Detector (GRaND) on board the NASA Dawn spacecraft provide constraints on the abundance and distribution of Fe, Ca, Al, Mg, and other rock‐forming elements. From a circular, polar low‐altitude mapping orbit, GRaND sampled the regolith to decimeter depths with a spatial resolution of about 300 km. At this spatial scale, the variation in neutron absorption is about seven times lower than that of the Moon. The observed variation is consistent with the range of absorption for howardite whole‐rock compositions, which further supports the connection between Vesta and the howardite, eucrite, and diogenite meteorites. We find a strong correlation between neutron absorption and the percentage of eucritic materials in howardites and polymict breccias, which enables petrologic mapping of Vesta's surface. The distribution of basaltic eucrite and diogenite determined from neutron absorption measurements is qualitatively similar to that indicated by visible and near infrared spectroscopy. The Rheasilvia basin and ejecta blanket has relatively low absorption, consistent with Mg‐rich orthopyroxene. Based on a combination of Fe and neutron absorption measurements, olivine‐rich lithologies are not detected on the spatial scales sampled by GRaND. The sensitivity of GRaND to the presence of mantle material is described and implications for the absence of an olivine signature are discussed. High absorption values found in Vesta's “dark” hemisphere, where exogenic hydrogen has accumulated, indicate that this region is richer in basaltic eucrite, representative of Vesta's ancient upper crust.     

Synthetic high-resolution near-IR spectra of the Sun for planetary data reductions made from ATMOS/Spacelab-3 and Atlas-3 data

We have constructed synthetic solar spectra for the 2302-4800 cm⁻¹ (2.08-4.34 μm) range, a spectral range where planetary objects mainly emit reflected sunlight, using ATMOS (Atmospheric Trace Molecule Spectroscopy)/Spacelab-3 and Atlas-3 spectra, of which resolution is 0.01 cm⁻¹. We adopted Voigt line profiles for the modeling of line shapes based on an atlas of line identifications compiled by Geller [Geller, M., 1992. Key to Identification of Solar Features. A High-Resolution Atlas of the Infrared Spectrum of the Sun and the Earth Atmosphere from Space. NASA Reference Publ. 1224, vol. III. NASA, Washington, DC, pp. 1-22], who derived solar line positions and intensities from contaminated high-resolution solar spectra obtained by ATMOS/Spacelab-3. Because the ATMOS spectra in these wavelength ranges are compromised by absorption lines of molecules existing in Earth's high-altitude atmosphere and in the compartment of the spacecraft, the direct use of these high-resolution solar spectra has been inconvenient for the data reductions of planetary spectra. We compared the synthetic solar spectra with the ATMOS spectra, and obtained satisfactory fits for the majority of the solar lines with the exception of abnormal lines, which do not fit with Voigt line profiles. From the model fits, we were able to determine Voigt line parameters for the majority of solar lines; and we made a list of the abnormal lines. We also constructed telluric-line-free solar spectra by manually eliminating telluric lines from the ATMOS spectra and filling the gaps with adjacent continua. These synthetic solar spectra will be useful to eliminate solar continua from spectra of planetary objects to extract their own intrinsic spectral features.