Analysis Of Recombinant Lines Research Articles

Non-LTE radio recombination line analysis towards H ii region G34.25+0.14

ABSTRACT The electron temperature $T^{*}_\mathrm{ e}$ of H ii regions in local thermodynamic equilibrium (LTE) is usually calculated based on the ratio of radio combination lines (RRLs) and continuum emission. In this work, the LTE $T^{*}_\mathrm{ e}$ in the H ii region G34.25+0.14, which is especially luminous and regarded as a prime target to investigate the physical properties of an H ii region, is obtained by analysing both RRLs and continuum in L band, and employing the correction factor $b_n^{*}$ to correct for non-LTE conditions. The LTE $T^{*}_\mathrm{ e}$ values in L band are calculated to be $2580\, {\rm K}$ for H i/OH/Recombination line survey (THOR) observations and $3690\, {\rm K}$ for Survey of Ionized Gas in our Galaxy, using the Arecibo telescope (SIGGMA), respectively. By employing a non-LTE correction, we derive Te of 8900 $\, {\rm K}$ and the corresponding $b^{*}_n$ values are calculated to be 1 and close to 1 in X band and C band, respectively. However, $b_n^{*}$ at L band (${\sim} 1.4\, {\rm GHz}$) is calculated as 4.2 and 2.4 for THOR and SIGGMA, suggesting that non-LTE corrections are necessary and significantly affect the results. This work demonstrates that the assumption of LTE to calculate $T^{*}_\mathrm{ e}$ is not valid for the observed transitions in L band, and hence, non-LTE corrections are needed. Furthermore, Ne for G34.25+0.14 is calculated from multiple bands independently, consistent with previous work. This study provides a method which could be used for other H ii regions to investigate their degree of departure from LTE.

Genome sequencing of rice subspecies and genetic analysis of recombinant lines reveals regional rapid visco analyser (RVA) associated loci

Genome sequencing of rice subspecies and genetic analysis of recombinant lines reveals regional rapid visco analyser (RVA) associated loci

Genome sequencing of rice subspecies and genetic analysis of recombinant lines reveals regional yield- and quality-associated loci

BackgroundTwo of the most widely cultivated rice strains are Oryza sativa indica and O. sativa japonica, and understanding the genetic basis of their agronomic traits is of importance for crop production. These two species are highly distinct in terms of geographical distribution and morphological traits. However, the relationship among genetic background, ecological conditions, and agronomic traits is unclear.ResultsIn this study, we performed the de novo assembly of a high-quality genome of SN265, a cultivar that is extensively cultivated as a backbone japonica parent in northern China, using single-molecule sequencing. Recombinant inbred lines (RILs) derived from a cross between SN265 and R99 (indica) were re-sequenced and cultivated in three distinct ecological conditions. We identify 79 QTLs related to 15 agronomic traits. We found that several genes underwent functional alterations when the ecological conditions were changed, and some alleles exhibited contracted responses to different genetic backgrounds. We validated the involvement of one candidate gene, DEP1, in determining panicle length, using CRISPR/Cas9 gene editing.ConclusionsThis study provides information on the suitable environmental conditions, and genetic background, for functional genes in rice breeding. Moreover, the public availability of the reference genome of northern japonica SN265 provides a valuable resource for plant biologists and the genetic improvement of crops.

The Long Path from QTL to Gene

The Long Path from QTL to Gene

New effective recombination coefficients for nebular N ii lines

Here we report new ${\it ab initio}$ calculations of the effective recombination coefficients for the \ion{N}{ii} recombination spectrum. We have taken into account the density dependence of the coefficients arising from the relative populations of the fine-structure levels of the ground state of the recombining ion, an elaboration that has not been attempted before for this ion, and it opens up the possibility of electron density determination via recombination line analysis. Photoionization cross-sections, bound state energies, and the oscillator strengths of \ion{N}{ii} with $n \leq 11$ and $l \leq 4$ have been obtained using the close-coupling R-matrix method in the intermediate coupling scheme. Photoionization data were computed that accurately map out the near-threshold resonances and were used to derive recombination coefficients, including radiative and dielectronic recombination. Also new is including the effects of dielectronic recombination via high-$n$ resonances lying between the $^2$P$^{\rm o}$\,$_{1/2}$ and $^2$P$^{\rm o}$\,$_{3/2}$ levels. The new calculations are valid for temperatures down to an unprecedentedly low level (approximately 100 K). The newly calculated effective recombination coefficients allow us to construct plasma diagnostics based on the measured strengths of the \ion{N}{ii} optical recombination lines (ORLs). The derived effective recombination coefficients are fitted with analytic formulae as a function of electron temperature for different electron densities. The dependence of the emissivities of the strongest transitions of \ion{N}{ii} on electron density and temperature is illustrated. Potential applications of the current data to electron density and temperature diagnostics for photoionized gaseous nebulae are discussed. We also present a method of determining electron temperature and density simultaneously.

Can X-rays provide a solution to the abundance discrepancy problem in photoionized nebulae?

Abstract We re-examine the well-known discrepancy between ionic abundances determined via the analysis of recombination lines (RLs) and collisionally excited lines (CELs). We show that abundance variations can be mimicked in a chemically homogeneous medium by the presence of dense (nH > rsim 104 cm−3) X-ray irradiated regions which present different ionization and temperature structures from those of the more diffuse medium they are embedded in, which is predominantly ionized by extreme-ultraviolet radiation. The presence of X-ray ionized dense clumps or filaments also naturally explains the lower temperatures often measured from O ii RLs and from the Balmer jump when compared to temperatures determined by CELs. We discuss the implications for abundances determined via the analysis of CELs and RLs and provide a simple analytical procedure to obtain upward corrections for CEL-determined abundance. While we show that the abundance discrepancy factor and the Balmer Jump temperature determined from observations of the Orion Nebula can simultaneously be reproduced by this model (implying upward corrections for CELs by a factor of 1.15), we find that the required X-ray fluxes exceed the known Orion's stellar and diffuse X-ray budget, if we assume that the clumps are located at the edge of the blister. We propose, however, that spatially resolved observations may be used to empirically test the model, and outline how the framework developed in this Letter may be applied in the future to objects with better constrained geometries (e.g. planetary nebulae).

The impact of divertor detachment on carbon sources in JET L-mode discharges

Hydrocarbon injection experiments have been performed to investigate the chemical sputtering yield of carbon-fibre composites at elevated temperatures ( T surface ≃ 500 K ) and detached plasma conditions in the JET outer divertor. A plasma scenario in L-mode with the outer strike-point positioned on the load bearing septum replacement plate was developed to detach the outer divertor leg and to provide the strong recombining target plasma. The operational window was explored in a set of discharges with strong deuterium puffing into the private-flux region. Langmuir probes showed a clear roll-over in the ion flux up to complete plasma detachment at the target plate during the density ramp of the discharge. Paschen recombination line analysis shows strong volume recombination with electron temperatures below 2.0 eV prior to the appearance of a radiation instability – an X-point Marfe. A strong reduction of the intrinsic CD photon flux was observed under these conditions, whereas local CD 4 injection still led to CD photon flux emission. This provides conclusive evidence for a reduction of the hydrocarbon flux and the chemical sputtering under detached plasma conditions.

Importance of the Secondary Genepool in Barley Genetics and Breeding. I. Cytogenetics and Molecular Analysis

There have been no plant breeding developments using species from the tertiary genepool of cultivated barley for breeding or genetics since the VIII<sup>th</sup> International Barley Genetics Symposium in 2000. Hence, the first part of this review describes progress since 2000 in developing and characterising recombinant lines derived from hybridisations between the sole species in the secondary genepool, Hordeum bulbosum L., and cultivated barley, Hordeum vulgare L. The topics discussed in part I are cytogenetics and molecular analysis of recombinant lines.  

QU Car: a very high luminosity nova-like binary with a carbon-enriched companion

QU Car is listed in cataclysmic variable star catalogues as a nova-like variable. This little-studied, yet bright interacting binary is re-appraised here in the light of new high-quality ultraviolet (UV) interstellar line data obtained with STIS on board the Hubble Space Telescope. The detection of a component of interstellar absorption at a mean LSR velocity of 14 km s 1 indicates that the distance to QU Car may be �2 kpc or more – a considerable increase on the previous lower-limiting distance of 500 pc. If so, the bolometric luminosity of QU Car could exceed 10 37 ergs s 1 . This would place this binary in the luminosity domain occupied by known compact-binary supersoft X-ray sources. Even at a 500 pc, QU Car appears to be the most luminous nova-like variable known. New intermediate dispersion optical spectroscopy of QU Car spanning 3800– 7000 u is presented. These data yield the discovery that Civ ��5801,12 is present as an unusually prominent emission line in an otherwise low-contrast line spectrum. Using measurements of this and other lines in a recombination line analysis, it is shown that the C/He abundance as proxied by the n(C 4+ )/n(He 2+ ) ratio may be as high as 0.06 (an order of magnitude higher than the solar ratio). Furthermore, the C/O abundance ratio is estimated to be greater than 1. These findings suggest that the companion in QU Car is a carbon star. If so, it would be the first example of a carbon star in such a binary. An early-type R star best matches the required abundance pattern and could escape detection at optical wavelengths provided the distance to QU Car is �2 kpc or more.

An empirical analysis of the stellar wind and Planetary Nebulae of the [WC10] central stars CPD–56° 8032 and He 2–113

[WC] stars are H–deficient central stars of PN which have developed a dense, fast stellar wind. Their spectra can mimic the spectra of massive (Min∼5OM⊙) Wolf-Rayet stars of the carbon sequence. Deriving their parameters is of importance both in understanding the PN and the Wolf-Rayet phenomena. Spectra of both objects were obtained at the AAT in May 1993 with the UCL Echelle Spectrograph (3500–9200 å, R=50,0000). The reddening, determined from comparing the Hβ nebular line fluxes with radio fluxes from Purton et al. (MNRAS 128, 321, 1982), yielded E(B-V)=0.68 (CPD–56° 8032) and 1.00 (He 2–113). Distances are derived using two different methods and they agree within the relative uncertainties. They are 1.35 and 1.50 kpc for CPD–56° 8032 and He 2–113, respectively. The electron temperatures of the C ii line formation region in the wind is derived from a recombination line analysis (20,000 and 17,000 K for CPD–56° 8032 and He 2–113, respectively). From the same stellar wind recombination line analysis, we find C/He=0.12 and 0.16, together with O/He=0.19 and 0.25, for CPD–56° 8032 and He 2–113 respectively.

Recombination line abundances in the winds of the [WC] Wolf-Rayet stars

We present a preliminary abundance analysis, utilising recombination theory, for the [WC] Wolf-Rayet central stars of the planetary nebulae NGC 6751 and NGC 6905. This analysis is based on optical spectrophotometry of a sample of [WC] stars which show a strong O vi 3811, 34 å feature in emission. We have performed a recombination line analysis of stellar wind emission lines which are judged to be optically thin, in order to derive relative C, O and He abundances. We also present a comparison of the derived wind abundances with those of Population I WO stars. For the [WC 4] central star of NGC 6751, we have derived C/He = 0.35 and C/O = 4.2, by number. And for the [WC 3] central star of NGC 6905, we have derived C/He = 0.36 and C/O< 12. These surface abundances are comparable to the abundances that have been derived for early type [WC] stars via more complex NLTE modelling (e.g. Koesterke & Hamann 1996).

The rich O II recombination spectrum of the planetary nebula NGC 7009: new observations and atomic data

We present new spectrophotometric observations of the rich O II optical recombination line spectrum of the planetary nubula NGC 7009, obtained at a spectral resolution of about 1 Å (FWHM). New intermediate coupling quantal calculations of O II radiative recombination coefficients for the 3d-3p and 4f-3d transitions are presented. The effect of departure from pure LS-coupling is shown to be important. Excellent agreement is found between the observed relative intensities of the O II lines and those calculated from recombination theory allowing for intermediate coupling effects. C, N and O abundances based on our recombination line measurements are derived. In all cases, they are about a factor of 5 higher than the corresponding values deduced from collisionally excited lines, indicating that the discrepancy between the abundances derived from these two different types of emission lines, previously known to exist for C2+, is a common phenomenon, and is probably caused by the same physical process. The nature of this process is still not known. If the discrepancy is due to temperature fluctuations, the implied rms temperature fluctuation prameter t2 is about a factor of 2 larger than that derived by comparing the temperatures deduced from the [O III] forbidden line ratio and from the ratio of the nebular continuum Balmer discontinuity to Hβ. However, if we adopted the electron temperature derived from nebular contiuum Balmer discontinuity instead of that from the [O III]forbidden line ratio, the C and N abundances deduced from ultraviolet collisionally excited lines would come into agreement with those deduced from the optical recombination lines, although the abundance of oxygen deduced from the optical forbidden lines would still be a factor of 2 lower than the corresponding value obtained from the optical recombination lines. The O/H abundance ratio derived from our recombination line analysis of NGC 7009 is more than a factor of 2 higher than the solar oxygen abundance.

Oxygen and carbon abundances for the WO stars

We present relative carbon and oxygen abundances derived via an optically thin recombination line analysis for five WO stars, and compare the derived abundances to recent evolutionary models. New recombination coefficients for O4+, O5+ and O6+ ions have allowed total oxygen abundances to be derived. The final C/He values range between 0.4 and 0.8 by number, consistent with C/He ratios previously derived for WC stars. O/He values range between 0.1 – 0.4, with C/O ratios between 2.1 – 4.8.

Infrared Observations of Mass Loss from Massive Stars

The future use of space-borne IR spectroscopy to determine the ionization structure and abundances in the outer winds of WR stars is described. A mass loss rate of 1.7×10-5 M⊙ yr–1 has been derived from 10 μm photometry of the WO2 star Sanduleak 5 (WR 142). The He/H number ratios in the winds of P Cyg and AG Car have been derived from a recombination line analysis of their 1-4 μm spectra and mass loss rates of 2.2×10-5 M⊙ yr–1 and 3.7×10-5 M⊙ yr–1 have been respectively derived for them.