The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Luigi Pontieri - One of the best experts on this subject based on the ideXlab platform.
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artificial selection on ant female caste ratio uncovers a link between female biased sex ratios and infection by wolbachia endosymbionts
Journal of Evolutionary Biology, 2017Co-Authors: Luigi Pontieri, Anna M Schmidt, Rohini Singh, Jes S Pedersen, Timothy A LinksvayerAbstract:Social insect sex and caste ratios are well-studied targets of evolutionary conflicts, but the heritable factors affecting these traits remain unknown. To elucidate these factors, we carried out a short-term artificial selection study on female caste ratio in the ant Monomorium pharaonis. Across three generations of bidirectional selection, we observed no response for caste ratio, but sex ratios rapidly became more female-biased in the two replicate high selection lines and less female-biased in the two replicate low selection lines. We hypothesized that this rapid divergence for sex ratio was caused by changes in the frequency of infection by the heritable bacterial endosymbiont Wolbachia, because the initial breeding stock varied for Wolbachia infection, and Wolbachia is known to cause female-biased sex ratios in other insects. Consistent with this hypothesis, the proportions of Wolbachia-infected colonies in the selection lines changed rapidly, mirroring the sex ratio changes. Moreover, the estimated effect of Wolbachia on sex ratio (~13% female bias) was similar in colonies before and during artificial selection, indicating that this Wolbachia effect is likely independent of the effects of artificial selection on other heritable factors. Our study provides evidence for the first case of endosymbiont sex ratio manipulation in a social insect.
D Dultzinhacyan - One of the best experts on this subject based on the ideXlab platform.
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searching for the physical drivers of the eigenvector 1 correlation space
The Astrophysical Journal, 2001Co-Authors: P Marziani, J W Sulentic, T Zwitter, D Dultzinhacyan, Massimo CalvaniAbstract:We recently discussed an Eigenvector 1 (E1) parameter space that provides optimal discrimination between the principal classes of broad-line active galactic nuclei (AGNs). In this paper we begin a search for the most important physical parameters that are likely to govern correlations and data point distribution in E1 space. We focus on the principal optical parameter plane involving the width of the Hβ broad component [FWHM(HβBC)] and the equivalent width ratio between the Fe II blend at 4570 A and HβBC. We show that the observed correlation for radio-quiet sources can be accounted for if it is primarily driven by the ratio of AGN luminosity to black hole mass (L/M ∝ Eddington ratio) convolved with source orientation. L/M apparently drives the radio-quiet correlation only for FWHM(Hβ) 4000 km s-1, which includes narrow-line Seyfert 1 galaxies and can be said to define an AGN "main sequence." Source orientation plays an increasingly important role as FWHM(HβBC) increases. We also argue that AGNs lying outside the radio-quiet main sequence, and specifically those with optical Fe II much stronger than expected for a given FWHM(HβBC), may all be broad absorption line QSOs.
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searching for the physical drivers of the eigenvector 1 correlation space
arXiv: Astrophysics, 2001Co-Authors: P Marziani, J W Sulentic, T Zwitter, D Dultzinhacyan, Massimo CalvaniAbstract:[Latex markup removed] We recently discussed an Eigenvector 1 (E1) parameter space that provides optimal discrimination between the principal classes of broad-line Active Galactic Nuclei (AGN). In this paper we begin a search for the most important physical parameters that are likely to govern correlations and data point distribution in E1 space. We focus on the principal optical parameter plane involving the width of the H-beta broad component and the equivalent width ratio between the FeII blend at 4570 A and H-beta broad component. We show that the observed correlation for radio-quiet sources can be accounted for if it is primarily driven by the ratio of AGN luminosity to black hole mass (L/M proportional to Eddington ratio) convolved with source orientation. L/M apparently drives the radio-quiet correlation only for FWHM(H-beta) < 4000 km/s which includes Narrow Line Seyfert 1 (NLSy1) galaxies and can be said to define an AGN ``main sequence.'' Source orientation plays an increasingly important role as FWHM(H-beta) increases. We also argue that AGN lying outside the radio-quiet ``main sequence,'' and specifically those with optical FeII much stronger than expected for a given FWHM(H-beta), may all be Broad Absorption Line QSOs.
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eigenvector 1 an optimal correlation space for active galactic nuclei
The Astrophysical Journal, 2000Co-Authors: J W Sulentic, P Marziani, T Zwitter, D DultzinhacyanAbstract:We identify a correlation space involving optical and UV emission-line parameters as well as the soft X-ray spectral index that provides optimal discrimination between all principal classes of active galactic nuclei (AGNs). Most of the sources in our three high-quality data samples show a strong intercorrelation with narrow-line Seyfert 1 (NLSy1) galaxies and steep-spectrum radio galaxies occupying opposite extrema in the space. NLSy1 sources show a clear continuity with broader line sources, indicating that they are not a disjoint class of AGN as is sometimes suggested. We interpret the principal intercorrelation in the parameter space as being driven by the AGN luminosity-to-black hole mass ratio (L/M is proportional to the Eddington ratio). Source orientation no doubt also plays an important role, but it is not yet clear whether FWHM Hβ or C IV λ1549 line shift is the better indicator. We tentatively identify two radio-quiet populations: an almost pure radio-quiet population A, with FWHM ≤ 4000, and population B, which occupies the same parameter domain as the flat-spectrum radio-loud sources. A possible interpretation sees population A/NLSy1 as lower mass/high accretion rate sources and population B/radio-loud sources as the opposite.
Timothy A Linksvayer - One of the best experts on this subject based on the ideXlab platform.
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artificial selection on ant female caste ratio uncovers a link between female biased sex ratios and infection by wolbachia endosymbionts
Journal of Evolutionary Biology, 2017Co-Authors: Luigi Pontieri, Anna M Schmidt, Rohini Singh, Jes S Pedersen, Timothy A LinksvayerAbstract:Social insect sex and caste ratios are well-studied targets of evolutionary conflicts, but the heritable factors affecting these traits remain unknown. To elucidate these factors, we carried out a short-term artificial selection study on female caste ratio in the ant Monomorium pharaonis. Across three generations of bidirectional selection, we observed no response for caste ratio, but sex ratios rapidly became more female-biased in the two replicate high selection lines and less female-biased in the two replicate low selection lines. We hypothesized that this rapid divergence for sex ratio was caused by changes in the frequency of infection by the heritable bacterial endosymbiont Wolbachia, because the initial breeding stock varied for Wolbachia infection, and Wolbachia is known to cause female-biased sex ratios in other insects. Consistent with this hypothesis, the proportions of Wolbachia-infected colonies in the selection lines changed rapidly, mirroring the sex ratio changes. Moreover, the estimated effect of Wolbachia on sex ratio (~13% female bias) was similar in colonies before and during artificial selection, indicating that this Wolbachia effect is likely independent of the effects of artificial selection on other heritable factors. Our study provides evidence for the first case of endosymbiont sex ratio manipulation in a social insect.
P Rafanelli - One of the best experts on this subject based on the ideXlab platform.
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parent population of flat spectrum radio loud narrow line seyfert 1 galaxies
Astronomy and Astrophysics, 2015Co-Authors: M Berton, L Foschini, S Ciroi, V Cracco, G La Mura, M L Lister, Smita Mathur, B M Peterson, J L Richards, P RafanelliAbstract:Flat-spectrum radio-loud narrow-line Seyfert 1 galaxies (NLS1s) are a recently discovered class ofγ-ray emitting Active Galactic Nuclei (AGN), that exhibit some blazar-like properties which are explained with the presence of a relativistic jet viewed at small angles. When blazars are observed at larger angles they appear as radio-galaxies, and we expect to observe an analogue parent population for beamed NLS1s. However, the number of known NLS1s with the jet viewed at large angles is not enough. Therefore, we tried to understand the origin of this deficit. Current hypotheses about the nature of parent sources are steep-spectrum radioloud NLS1s, radio-quiet NLS1s and disk-hosted radio-galaxies. To test these hypotheses we built three samples of candidate sources plus a control sample, and calculated their black hole mass and Eddington ratio using their optical spectra. We then performed a Kolmogorov-Smirnov statistical test to investigate the compatibility of our different samples with a beamed population. Our results indicate that, when the inclination angle increases, a beamed source appears as a steep-spectrum radio-loud NLS1, or possibly even as a disk-hosted radio-galaxy with low black hole mass and high Eddington ratio. Further investigations, involving larger complete samples and observations at radio frequency, are needed to understand the incidence of disk-hosted radio-galaxies in the parent population, and to assess whether radio-quiet NLS1s can play a role, as well.
J W Sulentic - One of the best experts on this subject based on the ideXlab platform.
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searching for the physical drivers of the eigenvector 1 correlation space
The Astrophysical Journal, 2001Co-Authors: P Marziani, J W Sulentic, T Zwitter, D Dultzinhacyan, Massimo CalvaniAbstract:We recently discussed an Eigenvector 1 (E1) parameter space that provides optimal discrimination between the principal classes of broad-line active galactic nuclei (AGNs). In this paper we begin a search for the most important physical parameters that are likely to govern correlations and data point distribution in E1 space. We focus on the principal optical parameter plane involving the width of the Hβ broad component [FWHM(HβBC)] and the equivalent width ratio between the Fe II blend at 4570 A and HβBC. We show that the observed correlation for radio-quiet sources can be accounted for if it is primarily driven by the ratio of AGN luminosity to black hole mass (L/M ∝ Eddington ratio) convolved with source orientation. L/M apparently drives the radio-quiet correlation only for FWHM(Hβ) 4000 km s-1, which includes narrow-line Seyfert 1 galaxies and can be said to define an AGN "main sequence." Source orientation plays an increasingly important role as FWHM(HβBC) increases. We also argue that AGNs lying outside the radio-quiet main sequence, and specifically those with optical Fe II much stronger than expected for a given FWHM(HβBC), may all be broad absorption line QSOs.
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searching for the physical drivers of the eigenvector 1 correlation space
arXiv: Astrophysics, 2001Co-Authors: P Marziani, J W Sulentic, T Zwitter, D Dultzinhacyan, Massimo CalvaniAbstract:[Latex markup removed] We recently discussed an Eigenvector 1 (E1) parameter space that provides optimal discrimination between the principal classes of broad-line Active Galactic Nuclei (AGN). In this paper we begin a search for the most important physical parameters that are likely to govern correlations and data point distribution in E1 space. We focus on the principal optical parameter plane involving the width of the H-beta broad component and the equivalent width ratio between the FeII blend at 4570 A and H-beta broad component. We show that the observed correlation for radio-quiet sources can be accounted for if it is primarily driven by the ratio of AGN luminosity to black hole mass (L/M proportional to Eddington ratio) convolved with source orientation. L/M apparently drives the radio-quiet correlation only for FWHM(H-beta) < 4000 km/s which includes Narrow Line Seyfert 1 (NLSy1) galaxies and can be said to define an AGN ``main sequence.'' Source orientation plays an increasingly important role as FWHM(H-beta) increases. We also argue that AGN lying outside the radio-quiet ``main sequence,'' and specifically those with optical FeII much stronger than expected for a given FWHM(H-beta), may all be Broad Absorption Line QSOs.
-
eigenvector 1 an optimal correlation space for active galactic nuclei
The Astrophysical Journal, 2000Co-Authors: J W Sulentic, P Marziani, T Zwitter, D DultzinhacyanAbstract:We identify a correlation space involving optical and UV emission-line parameters as well as the soft X-ray spectral index that provides optimal discrimination between all principal classes of active galactic nuclei (AGNs). Most of the sources in our three high-quality data samples show a strong intercorrelation with narrow-line Seyfert 1 (NLSy1) galaxies and steep-spectrum radio galaxies occupying opposite extrema in the space. NLSy1 sources show a clear continuity with broader line sources, indicating that they are not a disjoint class of AGN as is sometimes suggested. We interpret the principal intercorrelation in the parameter space as being driven by the AGN luminosity-to-black hole mass ratio (L/M is proportional to the Eddington ratio). Source orientation no doubt also plays an important role, but it is not yet clear whether FWHM Hβ or C IV λ1549 line shift is the better indicator. We tentatively identify two radio-quiet populations: an almost pure radio-quiet population A, with FWHM ≤ 4000, and population B, which occupies the same parameter domain as the flat-spectrum radio-loud sources. A possible interpretation sees population A/NLSy1 as lower mass/high accretion rate sources and population B/radio-loud sources as the opposite.
