24,289 research outputs found
Evidence for a Hard Ionizing Spectrum from a z=6.11 Stellar Population
We present the Magellan/FIRE detection of highly-ionized CIV 1550 and OIII]
1666 in a deep infrared spectrum of the z=6.11 gravitationally lensed low-mass
galaxy RXC J2248.7-4431-ID3, which has previously-known Lyman-alpha. No
corresponding emission is detected at the expected location of HeII 1640. The
upper limit on HeII paired with detection of OIII] and CIV constrains possible
ionization scenarios. Production of CIV and OIII] requires ionizing photons of
2.5-3.5 Ryd, but once in that state their multiplet emission is powered by
collisional excitation at lower energies (~0.5 Ryd). As a pure recombination
line, HeII emission is powered by 4 Ryd ionizing photons. The data therefore
require a spectrum with significant power at 3.5 Ryd but a rapid drop toward
4.0 Ryd. This hard spectrum with a steep drop is characteristic of
low-metallicity stellar populations, and less consistent with soft AGN
excitation, which features more 4 Ryd photons and hence higher HeII flux. The
conclusions based on ratios of metal line detections to Helium non-detection
are strengthened if the gas metallicity is low. RXJ2248-ID3 adds to the growing
handful of reionization-era galaxies with UV emission line ratios distinct from
the general z=2-3 population, in a way that suggests hard ionizing spectra that
do not necessarily originate in AGN.Comment: 7 pages, 4 figures, 1 table. Accepted for publication to ApJ
Comment on "Multiconfiguration Dirac-Fock energy levels and radiative rates for Br-like tungsten" by S. Aggarwal, A.K.S. Jha, and M. Mohan [Can . J. Phys. 91 (2013) 394]
We report calculations of energy levels and oscillator strengths for
transitions in W XL, undertaken with the general-purpose relativistic atomic
structure package ({\sc grasp}) and flexible atomic code ({\sc fac}).
Comparisons are made with existing results and the accuracy of the data is
assessed. Discrepancies with the most recent results of S. Aggarwal et al.
[Can. J. Phys. {\bf 91} (2013) 394] are up to 0.4 Ryd and up to two orders of
magnitude for energy levels and oscillator strengths, respectively.
Discrepancies for lifetimes are even larger, up to four orders of magnitude for
some levels. Our energy levels are estimated to be accurate to better than 0.5%
(i.e. 0.2 Ryd), whereas results for oscillator strengths and lifetimes should
be accurate to better than 20%.Comment: Text 7p, Tables 4, will appear in Canadian Journal of Physics (2013
Latitudinal clines in sexual selection, sexual size dimorphism, and sex-specific genetic dispersal during a poleward range expansion
Acknowledgements This work was supported by Macquarie University (to AC, RYD), an EU FP7, Marie Curie International Incoming Fellowship (to RYD, BH; project code âMOVE2ADAPTâ), a WennerGren Foundation Postdoctoral Stipend (to RYD, BH), the Oscar and Lili Lamm Foundation (to RYD, BH), Biodiversity and Ecosystem Services in a Changing Climate (BECC; a joint LundGothenburg University initiative) (to LL, BH), the Swedish Research Council (to EIS, BH (2014-5222, 2016-689)), the Crafoord Foundation, âStina Werners Stiftelseâ and âErik Philip Sörensens Stiftelseâ (to EIS). We thank Hanna Bensch, John Waller, Paul Caplat and Martin Andersson for field and lab assistance, the Grimsö Research Station and Mikael Ă
kesson for field support and Sonu Yadav for analysis advice. We thank Julian Catchen, Martin Stervander and Dag Ahren for bioinformatics advice and Maren Wellenreuther for helpful discussion.Peer reviewedPostprin
Energy levels, radiative rates, and lifetimes for transitions in W LVIII
Energy levels and radiative rates are reported for transitions in Cl-like W
LVIII. Configuration interaction (CI) has been included among 44 configurations
(generating 4978 levels) over a wide energy range up to 363 Ryd, and the
general-purpose relativistic atomic structure package ({\sc grasp}) adopted for
the calculations. Since no other results of comparable complexity are
available, calculations have also been performed with the flexible atomic code
({\sc fac}), which help in assessing the accuracy of our results. Energies are
listed for the lowest 400 levels (with energies up to 98 Ryd), which
mainly belong to the 3s3p, 3s3p, 3s3p3d,
3s3p3d, 3s3p3d, 3s3p3d, and 3p3d
configurations, and radiative rates are provided for four types of transitions,
i.e. E1, E2, M1, and M2. Our energy levels are assessed to be accurate to
better than 0.5%, whereas radiative rates (and lifetimes) should be accurate to
better than 20% for a majority of the strong transitions.Comment: About 12p of Text and 3 Tables which will be published in ADNDT
(2014
Radiative rates and electron impact excitation rates for transitions in He II
We report calculations of energy levels, radiative rates, collision
strengths, and effective collision strengths for transitions among the lowest
25 levels of the n <= 5 configurations of He~II. The general-purpose
relativistic atomic structure package (GRASP) and Dirac atomic R-matrix code
(DARC) are adopted for the calculations. Radiative rates, oscillator strengths,
and line strengths are reported for all electric dipole (E1), magnetic dipole
(M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among
the 25 levels. Furthermore, collision strengths and effective collision
strengths are listed for all 300 transitions among the above 25 levels over a
wide energy (temperature) range up to 9 Ryd (10**5.4 K). Comparisons are made
with earlier available results and the accuracy of the data is assessed.Comment: 30 pages of text including 12 figures and 5 Tables will appear in
ATOMS 5 (2017
Signatures of local adaptation along environmental gradients in a range-expanding damselfly (Ischnura elegans)
ACKNOWLEDGEMENTSThis work was supported by an EU FP7, Marie Curie International Incoming Fellowship (to RYD; project code âMOVE2ADAPTâ), a Wenner-Gren Foundation Postdoctoral Stipend (to RYD), the Oscar and Lili Lamm Foundation (to RYD, BH), Biodiversity and Ecosystem Services in a Changing Climate (BECC; a joint LundâGothenburg University initiative) (LL), the Swedish Research Council (EIS, BH),the Crafoord Foundation (EIS, BH) and Erik Philip-Sorensens Stiftelse (E.I.S.). We would like to thank Hanna Bensch and Paul Caplat for assistance with the collection of samples in the field and the Grimso Research Station and Mikael Akesson for logistical support. Wethank Pallavi Chauhan for assistance with SNP annotation. We thank Martin Andersson for assistance with DNA extraction, Jane Jonssonfor laboratory administration, and Julian Catchen, Martin Stervander, Dag Ahren and Maren Wellenreuther for bioinformatics advice and helpful discussion.Peer reviewedPostprin
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