| 1. |
- Laursen, Peter Nørkjær, et al.
(författare)
-
Comparison between patients included in randomized controlled trials of ischemic heart disease and real-world data. A nationwide study
- 2018
-
Ingår i: American Heart Journal. - : Elsevier BV. - 0002-8703. ; 204, s. 128-138
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The objective was to compare patients with ischemic heart disease (IHD) undergoing percutaneous coronary intervention (PCI) who were included in randomized controlled trials (RCTs) (trial participants) with patients who were not included (nonparticipants) on a trial-by-trial basis and according to indication for PCI. Methods: In this cohort study, we compared patients with IHD who were randomized in RCTs in relation to undergoing PCI in Denmark between 2011 and 2015 were considered as RCT-participants in this study. The RCT-participants were compared with contemporary nonparticipants with IHD undergoing PCI in the same period, and they were identified using unselected national registry data. The primary end point was all-cause mortality. Results: A total of 10,317 (30%) patients were included in 10 relevant RCTs (trial participants), and a total of 23,644 (70%) contemporary patients did not participate (nonparticipants). In all the included RCTs, nonparticipants had higher hazard ratios for mortality compared to trial participants (P <.001). Among all patients treated with PCI, the pooled estimates showed a significantly higher mortality rate for nonparticipants compared to trial participants (hazard ratio: 2.03, 95% CI: 1.88-2.19) (P <.001). When patients were stratified according to indication for PCI, the pooled estimates showed a significantly lower mortality rate for trial participants compared to nonparticipants in all strata (P for all <.001). Conclusions: Trial participants in recently performed RCTs including patients undergoing PCI were not representative of the general population of patients with IHD treated with PCI according to clinical characteristics and mortality. The difference in mortality was found irrespective of the indication for PCI. Thus, results from RCTs including patients undergoing PCI should be extrapolated with caution to the general patient population.
|
|
| 2. |
- Laursen, Peter Nørkjær, et al.
(författare)
-
Unreported exclusion and sampling bias in interpretation of randomized controlled trials in patients with STEMI
- 2019
-
Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273. ; 289, s. 1-5
-
Tidskriftsartikel (refereegranskat)abstract
- Aims: To assess the impact of sampling bias due to reported as well as unreported exclusion of the target population in a multi-center randomized controlled trial (RCT)of ST-elevation myocardial infarction (STEMI). Methods and Results: We compared clinical characteristics and mortality between participants in the DANAMI-3 trial to contemporary non-participants with STEMI using unselected registries. A total of 179 DANAMI-3 participants (8%)and 617 contemporary non-participants (22%)had died (Log-Rank: P < 0.001)after a median follow-up of 1333 days (range: 1–2021 days). In an unadjusted Cox regression model all groups of non-participants had a higher hazard ratio to predict mortality compared to participants: eligible excluded (n = 144)(hazard ratio: 3.41 (95% CI: (2.69–4.32)), ineligible excluded (n = 472)(hazard ratio: 3.42 (95% CI: (2.44–4.80), eligible non-screened (n = 154)(hazard ratio: 3.37 (95% CI: (2.36–4.82)), ineligible non-screened (n = 154)(hazard ratio: 6.48 (95% CI: (4.77–8.80). Conclusion: Sampling bias had occurred due to both reported and unreported exclusion of eligible patients and the difference in mortality between participants and non-participants could not be explained only by the trial exclusion criteria. Thus, screening logs may not be suited to address the risks of sampling bias.
|
|
| 3. |
- Zamora, Juan Carlos, et al.
(författare)
-
Considerations and consequences of allowing DNA sequence data as types of fungal taxa
- 2018
-
Ingår i: IMA Fungus. - : INT MYCOLOGICAL ASSOC. - 2210-6340 .- 2210-6359. ; 9:1, s. 167-185
-
Tidskriftsartikel (refereegranskat)abstract
- Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.
|
|
| 4. |
- Biasin, Elisa, et al.
(författare)
-
Anisotropy enhanced X-ray scattering from solvated transition metal complexes
- 2018
-
Ingår i: Journal of Synchrotron Radiation. - 0909-0495. ; 25:2, s. 306-315
-
Tidskriftsartikel (refereegranskat)abstract
- Time-resolved X-ray scattering patterns from photoexcited molecules in solution are in many cases anisotropic at the ultrafast time scales accessible at X-ray free-electron lasers (XFELs). This anisotropy arises from the interaction of a linearly polarized UV-Vis pump laser pulse with the sample, which induces anisotropic structural changes that can be captured by femtosecond X-ray pulses. In this work, a method for quantitative analysis of the anisotropic scattering signal arising from an ensemble of molecules is described, and it is demonstrated how its use can enhance the structural sensitivity of the time-resolved X-ray scattering experiment. This method is applied on time-resolved X-ray scattering patterns measured upon photoexcitation of a solvated di-platinum complex at an XFEL, and the key parameters involved are explored. It is shown that a combined analysis of the anisotropic and isotropic difference scattering signals in this experiment allows a more precise determination of the main photoinduced structural change in the solute, i.e. the change in Pt - Pt bond length, and yields more information on the excitation channels than the analysis of the isotropic scattering only. Finally, it is discussed how the anisotropic transient response of the solvent can enable the determination of key experimental parameters such as the instrument response function.The analysis of time-resolved X-ray scattering patterns collected at an XFEL upon photoexcitation of a di-platinum complex in solution is described. The analysis quantitatively considers the anisotropy of the signal.
|
|
| 5. |
- Bridge, Joanna S., et al.
(författare)
-
The Ly alpha Reference Sample. VIII. Characterizing Ly alpha Scattering in Nearby Galaxies
- 2018
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 852:1
-
Tidskriftsartikel (refereegranskat)abstract
- We examine the dust geometry and Ly alpha scattering in the galaxies of the Lyman Alpha Reference Sample (LARS), a set of 14 nearby (0.02 < z < 0.2) Ly alpha-emitting and starbursting systems with Hubble Space Telescope Ly alpha, H alpha, and H beta imaging. We find that the global dust properties determined by line ratios are consistent with other studies, with some of the LARS galaxies exhibiting clumpy dust media, while others of them show significantly lower Ly alpha emission compared to their Balmer decrement. With the LARS imaging, we present Ly alpha/H alpha and H alpha/H beta maps with spatial resolutions as low as similar to 40 pc, and use these data to show that in most galaxies, the dust geometry is best modeled by three distinct regions: a central core where dust acts as a screen, an annulus where dust is distributed in clumps, and an outer envelope where Ly alpha photons only scatter. We show that the dust that affects the escape of Ly alpha is more restricted to the galaxies' central regions, while the larger Ly alpha halos are generated by scattering at large radii. We present an empirical modeling technique to quantify how much Ly alpha scatters in the halo, and find that this characteristic scattering distance correlates with the measured size of the Ly alpha halo. We note that there exists a slight anti-correlation between the scattering distance of Ly alpha and global dust properties.
|
|
| 6. |
- Christensen, Lise, et al.
(författare)
-
Gravitationally lensed galaxies at 2 < z < 3.5 : direct abundance measurements of Ly alpha emitters
- 2012
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 427:3, s. 1973-1982
-
Tidskriftsartikel (refereegranskat)abstract
- Strong gravitational lensing magnifies the flux from distant galaxies, allowing us to detect emission lines that would otherwise fall below the detection threshold for medium-resolution spectroscopy. Here we present the detection of temperature-sensitive oxygen emission lines from three galaxies at 2 ? z ? 3.5, which enables us to directly determine the oxygen abundances and thereby double the number of galaxies at z > 2 for which this has been possible. The three galaxies have similar to 10?per?cent solar oxygen abundances in agreement with strong emission-line diagnostics. Carbon and nitrogen ratios relative to oxygen are subsolar as expected for young metal-poor galaxies. Two of the galaxies are Lyman a (Lya) emitters with rest-frame equivalent widths of 20 and 40 angstrom, respectively, and their high magnification factors allow us for the first time to gain insight into the physical characteristics of high-redshift Lya emitters. Using constraints from the physical properties of the galaxies, we accurately reproduce their line profiles with radiative transfer models. The models show a relatively small outflow in agreement with the observed small velocity offsets between nebular emission and interstellar absorption lines.
|
|
| 7. |
- Christensen, Lise, et al.
(författare)
-
The low-mass end of the fundamental relation for gravitationally lensed star-forming galaxies at 1 < z < 6
- 2012
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 427:3, s. 1953-1972
-
Forskningsöversikt (refereegranskat)abstract
- We present Very Large Telescope/X-shooter spectra of 13 galaxies in the redshift range 1 ? z ? 6, which are strongly lensed by massive galaxy clusters. Spectroscopic redshifts are measured for nine galaxies, while three sources have redshifts determined from continuum breaks in their spectra. The stellar masses of the galaxies span four orders of magnitude between 107 and 1011?M? and have luminosities at 1500 angstrom rest frame between 0.004 and 9L* after correcting for the magnification. This allows us to probe a variety of galaxy types from young, low-mass starburst galaxies to massive evolved galaxies. The lensed galaxies with stellar masses less than 1010?M? have a large scatter compared to the fundamental relation between stellar mass, star formation rates and oxygen abundances. We provide a modified fit to the fundamental relation for low-mass, low-metallicity galaxies with a weaker dependence of the metallicity on either the star formation rate or stellar mass compared to low-redshift, high-mass and high-metallicity Sloan Digital Sky Survey galaxies.
|
|
| 8. |
- Christiansen, Maja, et al.
(författare)
-
Protein chemical characterization of Gc globulin (vitamin D-binding protein) isoforms; Gc-1f, Gc-1s and Gc-2.
- 2007
-
Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 1878-2434. ; 1774:4
-
Tidskriftsartikel (refereegranskat)abstract
- Gc globulin, also called vitamin D-binding protein, is a plasma protein involved in the extracellular actin-scavenger system, vitamin D transport and possibly also other biological activities. Low levels of Gc globulin have been found to correlate with multiple organ failure and non-survival of patients with fulminant hepatic failure and trauma. Here, we characterize the dominant isoforms of plasma-derived Gc globulin from Cohn fraction IV paste with respect to amino acid sequence and posttranslational modifications. Gc globulin was purified in large scale and the isoforms separated by ion exchange chromatography. The separated isoforms and several commercial preparations of individual isoforms were characterized by mass spectrometry. This revealed that the major isoforms were non-glycosylated. Compared to the Gc-1f isoform the other dominating isoforms represented an Asp/Glu substitution (Gc-1s) and a Thr/Lys substitution (Gc-2) in agreement with DNA sequencing studies. The commercial preparations were found to represent mainly one or two isoforms. An O-linked glycan with a mass of 656 Da and terminating with a sialic acid residue was detected on a minor proportion of Gc globulin molecules.
|
|
| 9. |
- Duval, Florent, et al.
(författare)
-
The Lyman alpha reference sample VI. Lyman alpha escape from the edge-on disk galaxy Mrk 1486
- 2016
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 587
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Recent numerical simulations suggest that the strength of the Lyman alpha (Ly alpha) line of star-forming disk galaxies strongly depends on the inclination at which they are observed: from edge-on to face-on, we expect to see a change from a strongly attenuated Ly alpha line to a strong Ly alpha emission line.Aims. We aim to understand how a strong Ly alpha emission line is able to escape from the low-redshift highly inclined (edge-on) disk galaxy Mrk 1486 (z similar to 0.0338). To our knowledge, this work is the first observational study of Ly alpha transport inside an edge-on disk galaxy.Methods. Using a large set of HST imaging and spectroscopic data, we investigated the interstellar medium (ISM) structure and the dominant source of Ly alpha radiation inside Mrk 1486. Moreover, using a 3D Monte Carlo Ly alpha radiation transfer code, we studied the radiative transfer of Ly alpha and UV continuum photons inside a 3D geometry of neutral hydrogen (HI) and dust that models the ISM structure at the galaxy center. Our numerical simulations predicted the Ly alpha line profile that we then compared to the one observed in the HST/COS spectrum of Mrk 1486.Results. While a pronounced Ly alpha absorption line emerges from the disk of Mrk 1486, very extended Ly alpha structures are observed at large radii from the galaxy center: a large Ly alpha-halo and two very bright Ly alpha regions located slightly above and below the disk plane. The analysis of IFU H alpha spectroscopic data of Mrk 1486 indicates the presence of two bipolar outflowing halos of HI gas at the same location as these two bright Ly alpha regions. Comparing different diagnostic diagrams (such as [OIII](5007)/H beta versus [OI](6300)/H alpha) to photo-and shock-ionization models, we find that the Ly alpha production of Mrk 1486 is dominated by photoionization inside the galaxy disk. From this perspective, our numerical simulations succeed in reproducing the strength and shape of the observed Ly alpha emission line of Mrk 1486 by assuming a scenario in which the Ly alpha photons are produced inside the galaxy disk, travel along the outflowing halos, and scatter on cool HI materials toward the observer.Conclusions. Extended bipolar galactic winds are frequently observed from star-forming disk galaxies. Given the advantage Ly alpha photons take of such outflowing HI materials to easily escape from Mrk 1486, this mechanism may explain the origin of strong Ly alpha emission lines frequently observed from highly inclined galaxies at high-redshift. This therefore challenges the robustness of the expected viewing-angle effect on the Ly alpha properties of star-forming disk galaxies.
|
|
| 10. |
- Ekroos, Johan, et al.
(författare)
-
Declines amongst breeding Eider Somateria mollissima numbers in the Baltic/Wadden Sea flyway
- 2012
-
Ingår i: Ornis Fennica. - 0030-5685. ; 89:2, s. 81-90
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the status of the Baltic/Wadden Sea flyway Eider population based on trends in breeding and wintering numbers throughout the region, supplemented by changes in the sex ratio and proportion of young Eiders as monitored in the Danish hunting bag. At the flyway scale, total numbers of breeding pairs decreased by 48% during 2000-2009, after relatively stable breeding numbers in 1991-2000. The majority of the population nest in Finland and Sweden, where the number of breeding pairs has halved over the same period. After initial declines in winter numbers between 1991 and 2000, during 2000-2009, national wintering numbers increased in the Baltic Sea, but decreased in the Wadden Sea. The annual proportion of adult females in the Danish hunting bag data decreased from ca. 45% (1982) to ca. 25% (2009) and simultaneously the proportion of first-winter birds fell from ca. 70% to ca. 30%, indicating dramatic structural changes in the Danish wintering numbers. These results suggest that the total flyway population will experience further declines, unless productivity increases and the factors responsible for decreasing adult female survival are identified and ameliorated. We discuss potential population drivers and present some recommendations for improved flyway-level monitoring and management of Eiders.
|
|
| 11. |
- Fynbo, J. P. U., et al.
(författare)
-
Galaxy counterparts of metal-rich damped Ly alpha absorbers - II. A solar-metallicity and dusty DLA at z(abs)=2.58
- 2011
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 413:4, s. 2481-2488
-
Tidskriftsartikel (refereegranskat)abstract
- This is the second paper of a series reporting on the results from a survey conducted with the ESO VLT/X-shooter spectrograph. We target high-metallicity damped Lyman alpha absorbers (DLAs) with the aim of investigating the relation between galaxies detected in emission and those detected in absorption. Here, we report on the discovery of the galaxy counterpart of the z(abs) = 2.58 DLA on the line-of-sight to the z = 3.07 quasar SDSS J 091826.16+163609.0 (hereafter Q 0918+1636). The galaxy counterpart of the DLA is detected in the [O iii] lambda 5007 and [O ii] lambda lambda 3726, 3729 emission lines redshifted into the NIR at an impact parameter of 2.0 arcsec (16 kpc at z = 2.58). Ly alpha emission is not detected down to a 3 Sigma detection limit of 5 x 10-18 erg s-1 cm-2, which, compared to the strength of the oxygen lines, implies that Ly alpha emission from this galaxy is suppressed by more than an order of magnitude. The DLA has one of the highest metallicities measured so far at comparable redshifts. We find evidence for substantial depletion of refractory elements on to dust grains. Fitting the main metal line component of the DLA, which is located at z(abs) = 2.5832, we measure the metal abundances from Zn ii, S ii, Si ii, Cr ii, Mn ii, Fe ii and Ni ii to be -0.12 +/- 0.05, -0.26 +/- 0.05, -0.46 +/- 0.05, -0.88 +/- 0.05, -0.92 +/- 0.05, -1.03 +/- 0.05 and -0.78 +/- 0.05, respectively. In addition, we detect absorption in the Lyman and Werner bands of molecular hydrogen (H(2)), which represents the first detection of H(2) molecules with X-shooter. The background quasar Q 0918+1636 is amongst the reddest QSOs at redshifts 3.02 < z < 3.12 from the SDSS catalogue. Its UV to NIR spectrum is well fitted by a composite QSO spectrum reddened by SMC-/LMC-like extinction curves at z(abs) = 2.58 with a significant amount of extinction given by A(V) approximate to 0.2 mag. This supports previous claims that there may be more metal-rich DLAs missing from current samples due to dust reddening of the background QSOs. The fact that there is evidence for dust both in the central emitting regions of the galaxy (as evidenced by the lack of Ly alpha emission) and at an impact parameter of 16 kpc (as probed by the DLA) suggests that dust is widespread in this system.
|
|
| 12. |
- Fynbo, J. P. U., et al.
(författare)
-
Galaxy counterparts of metal-rich damped Lyman-alpha absorbers - II. A solar-metallicity and dusty DLA at z_abs=2.58
- 2010
-
Annan publikation (populärvet., debatt m.m.)abstract
- [Abridged]. Here, we report on the discovery of the galaxy counterpart of the z_abs=2.58 DLA on the line-of-sight to the z=3.07 quasar SDSS J091826.16+163609.0. The galaxy counterpart of the DLA is detected in the OIII 5007 and OII 3726,3729 emission lines redshifted into the NIR at an impact parameter of 16 kpc. Ly-alpha emission is not detected. The upper limit implies that Ly-alpha emission from this galaxy is suppressed by more than an order of magnitude. The DLA is amongst the most metal-rich DLAs studied so far at comparable redshifts. We find evidence for substantial depletion of refractory elements onto dust grains. Fitting the main metal line component of the DLA, which is located at z_abs=2.5832 and accounts for at least 85% of the total column density of low-ionisation species, we measure metal abundances from ZnII, SII, SiII, CrII, MnII, FeII and NiII of -0.12, -0.26, -0.46, -0.88, -0.92, -1.03 and -0.78, respectively. In addition, we detect absorption in the Lyman and Werner bands of hydrogen, which represents the first detection of H_2 molecules with X-shooter. The background quasar Q0918+1636 is amongst the reddest QSOs at redshifts 3.02<3.12 from the SDSS catalogue. Its UV to NIR spectrum is well fitted by a composite QSO spectrum reddened by SMC/LMC-like extinction curves at z_abs=2.58 with a significant amount of extinction given by A_V = 0.2 mag. This supports previous claims that there may be more metal-rich DLAs missing from current samples due to dust reddening of the background QSOs. The fact that there is evidence for dust both in the central emitting regions of the galaxy (as evidenced by the lack of Ly-alpha emission) and at an impact parameter of 16 kpc (as probed by the DLA) suggests that dust is widespread in this system.
|
|
| 13. |
- Haldrup, Kristoffer, et al.
(författare)
-
Ultrafast X-Ray Scattering Measurements of Coherent Structural Dynamics on the Ground-State Potential Energy Surface of a Diplatinum Molecule
- 2019
-
Ingår i: Physical Review Letters. - 0031-9007. ; 122:6
-
Tidskriftsartikel (refereegranskat)abstract
- We report x-ray free electron laser experiments addressing ground-state structural dynamics of the diplatinum anion Pt2POP4 following photoexcitation. The structural dynamics are tracked with <100 fs time resolution by x-ray scattering, utilizing the anisotropic component to suppress contributions from the bulk solvent. The x-ray data exhibit a strong oscillatory component with period 0.28 ps and decay time 2.2 ps, and structural analysis of the difference signal directly shows this as arising from ground-state dynamics along the PtPt coordinate. These results are compared with multiscale Born-Oppenheimer molecular dynamics simulations and demonstrate how off-resonance excitation can be used to prepare a vibrationally cold excited-state population complemented by a structure-dependent depletion of the ground-state population which subsequently evolves in time, allowing direct tracking of ground-state structural dynamics.
|
|
| 14. |
- Hayes, Matthew, et al.
(författare)
-
THE LYMAN ALPHA REFERENCE SAMPLE : EXTENDED LYMAN ALPHA HALOS PRODUCED AT LOW DUST CONTENT
- 2013
-
Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 765:2, s. L27-
-
Tidskriftsartikel (refereegranskat)abstract
- We report on new imaging observations of the Lyman alpha emission line (Ly alpha), performed with the Hubble Space Telescope, that comprise the backbone of the Lyman alpha Reference Sample. We present images of 14 starburst galaxies at redshifts 0.028 < z < 0.18 in continuum-subtracted Ly alpha, H alpha, and the far ultraviolet continuum. We show that Ly alpha is emitted on scales that systematically exceed those of the massive stellar population and recombination nebulae: as measured by the Petrosian 20% radius, RP20, Ly alpha radii are larger than those of H alpha by factors ranging from 1 to 3.6, with an average of 2.4. The average ratio of Ly alpha-to-FUV radii is 2.9. This suggests that much of the Ly alpha light is pushed to large radii by resonance scattering. Defining the Relative Petrosian Extension of Ly alpha compared to H alpha, xi(Ly alpha) = R-P20(Ly alpha)/R-P20(H alpha), we find xi(Ly alpha) to be uncorrelated with total Ly alpha luminosity. However, xi(Ly alpha) is strongly correlated with quantities that scale with dust content, in the sense that a low dust abundance is a necessary requirement (although not the only one) in order to spread Ly alpha photons throughout the interstellar medium and drive a large extended Ly alpha halo.
|
|
| 15. |
- Hayes, Matthew, et al.
(författare)
-
THE LYMAN ALPHA REFERENCE SAMPLE. II. HUBBLE SPACE TELESCOPE IMAGING RESULTS, INTEGRATED PROPERTIES, AND TRENDS
- 2014
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 782:1
-
Tidskriftsartikel (refereegranskat)abstract
- We report new results regarding the Ly alpha output of galaxies, derived from the Lyman Alpha Reference Sample, and focused on Hubble Space Telescope imaging. For 14 galaxies we present intensity images in Ly alpha, H alpha, and UV, and maps of H alpha/H beta, Ly alpha equivalent width (EW), and Ly alpha/H alpha. We present Ly alpha and UV radial light profiles and show they are well-fitted by Sersic profiles, but Ly alpha profiles show indices systematically lower than those of the UV (n approximate to 1-2 instead of greater than or similar to 4). This reveals a general lack of the central concentration in Ly alpha that is ubiquitous in the UV. Photometric growth curves increase more slowly for Ly alpha than the far ultraviolet, showing that small apertures may underestimate the EW. For most galaxies, however, flux and EW curves flatten by radii approximate to 10 kpc, suggesting that if placed at high-z only a few of our galaxies would suffer from large flux losses. We compute global properties of the sample in large apertures, and show total Ly alpha luminosities to be independent of all other quantities. Normalized Ly alpha throughput, however, shows significant correlations: escape is found to be higher in galaxies of lower star formation rate, dust content, mass, and nebular quantities that suggest harder ionizing continuum and lower metallicity. Six galaxies would be selected as high-z Ly alpha emitters, based upon their luminosity and EW. We discuss the results in the context of high-z Ly alpha and UV samples. A few galaxies have EWs above 50 angstrom, and one shows f(esc)(Ly alpha) of 80%; such objects have not previously been reported at low-z.
|
|
| 16. |
- Herenz, Edmund Christian, et al.
(författare)
-
The Lyman alpha reference sample VII. Spatially resolved H alpha kinematics
- 2016
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 587
-
Tidskriftsartikel (refereegranskat)abstract
- We present integral field spectroscopic observations with the Potsdam Multi-Aperture Spectrophotometer of all 14 galaxies in the z similar to 0.1 Lyman Alpha Reference Sample (LARS). We produce 2D line-of-sight velocity maps and velocity dispersion maps from the Balmer alpha (H alpha) emission in our data cubes. These maps trace the spectral and spatial properties of the LARS galaxies' intrinsic Ly alpha radiation field. We show our kinematic maps that are spatially registered onto the Hubble Space Telescope H alpha and Lyman alpha (Ly alpha) images. We can conjecture a causal connection between spatially resolved H alpha kinematics and Ly alpha photometry for individual galaxies, however, no general trend can be established for the whole sample. Furthermore, we compute the intrinsic velocity dispersion sigma(0), the shearing velocity v(shear), and the v(shear)/sigma(0) ratio from our kinematic maps. In general LARS galaxies are characterised by high intrinsic velocity dispersions (54 km s(-1) median) and low shearing velocities (65 km s(-1) median). The v(shear/sigma 0) values range from 0.5 to 3.2 with an average of 1.5. It is noteworthy that five galaxies of the sample are dispersion-dominated systems with v(shear)/sigma(0) < 1, and are thus kinematically similar to turbulent star-forming galaxies seen at high redshift. When linking our kinematical statistics to the global LARS Ly alpha properties, we find that dispersion-dominated systems show higher Ly alpha equivalent widths and higher Ly alpha escape fractions than systems with v(shear)/sigma(0) > 1. Our result indicates that turbulence in actively star-forming systems is causally connected to interstellar medium conditions that favour an escape of Ly alpha radiation.
|
|
| 17. |
- Jensen, Hannes, et al.
(författare)
-
On the use of Ly alpha emitters as probes of reionization
- 2013
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 428:2, s. 1366-1381
-
Tidskriftsartikel (refereegranskat)abstract
- We use numerical simulations to study the effects of the patchiness of a partly reionized intergalactic medium (IGM) on the observability of Ly alpha emitters (LAEs) at high redshifts (z greater than or similar to 6). We present a new model that divides the Ly alpha radiative transfer into a (circum) galactic and an extragalactic (IGM) part, and investigate how the choice of intrinsic line model affects the IGM transmission results. We use our model to study the impact of neutral hydrogen on statistical observables such as the Ly alpha rest-frame equivalent width (REW) distribution, the LAE luminosity function and the two-point correlation function. We find that if the observed changes in LAE luminosity functions and equivalent width distributions between z similar to 6 and 7 are to be explained by an increased IGM neutral fraction alone, we require an extremely late and rapid reionization scenario, where the Universe was similar to 40 per cent ionized at z = 7, similar to 50 per cent ionized at z = 6.5 and similar to 100 per cent ionized at z = 6. This is in conflict with other observations, suggesting that intrinsic LAE evolution at z greater than or similar to 6 cannot be completely neglected. We show how the two-point correlation function can provide more robust constraints once future observations obtain larger LAE samples, and provide predictions for the sample sizes needed to tell different reionization scenarios apart.
|
|
| 18. |
|
|
| 19. |
- Kjær, Kasper S., et al.
(författare)
-
Finding intersections between electronic excited state potential energy surfaces with simultaneous ultrafast X-ray scattering and spectroscopy
- 2019
-
Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 10:22, s. 5749-5760
-
Tidskriftsartikel (refereegranskat)abstract
- Light-driven molecular reactions are dictated by the excited state potential energy landscape, depending critically on the location of conical intersections and intersystem crossing points between potential surfaces where non-adiabatic effects govern transition probabilities between distinct electronic states. While ultrafast studies have provided significant insight into electronic excited state reaction dynamics, experimental approaches for identifying and characterizing intersections and seams between electronic states remain highly system dependent. Here we show that for 3d transition metal systems simultaneously recorded X-ray diffuse scattering and X-ray emission spectroscopy at sub-70 femtosecond time-resolution provide a solid experimental foundation for determining the mechanistic details of excited state reactions. In modeling the mechanistic information retrieved from such experiments, it becomes possible to identify the dominant trajectory followed during the excited state cascade and to determine the relevant loci of intersections between states. We illustrate our approach by explicitly mapping parts of the potential energy landscape dictating the light driven low-to-high spin-state transition (spin crossover) of [Fe(2,2′-bipyridine)3]2+, where the strongly coupled nuclear and electronic dynamics have been a source of interest and controversy. We anticipate that simultaneous X-ray diffuse scattering and X-ray emission spectroscopy will provide a valuable approach for mapping the reactive trajectories of light-triggered molecular systems involving 3d transition metals.
|
|
| 20. |
- Kjær, Kasper S., et al.
(författare)
-
Solvent control of charge transfer excited state relaxation pathways in [Fe(2,2′-bipyridine)(CN)4]2-
- 2018
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 20:6, s. 4238-4249
-
Tidskriftsartikel (refereegranskat)abstract
- The excited state dynamics of solvated [Fe(bpy)(CN)4]2-, where bpy = 2,2′-bipyridine, show significant sensitivity to the solvent Lewis acidity. Using a combination of optical absorption and X-ray emission transient spectroscopies, we have previously shown that the metal to ligand charge transfer (MLCT) excited state of [Fe(bpy)(CN)4]2- has a 19 picosecond lifetime and no discernable contribution from metal centered (MC) states in weak Lewis acid solvents, such as dimethyl sulfoxide and acetonitrile.1,2 In the present work, we use the same combination of spectroscopic techniques to measure the MLCT excited state relaxation dynamics of [Fe(bpy)(CN)4]2- in water, a strong Lewis acid solvent. The charge-transfer excited state is now found to decay in less than 100 femtoseconds, forming a quasi-stable metal centered excited state with a 13 picosecond lifetime. We find that this MC excited state has triplet (3MC) character, unlike other reported six-coordinate Fe(ii)-centered coordination compounds, which form MC quintet (5MC) states. The solvent dependent changes in excited state non-radiative relaxation for [Fe(bpy)(CN)4]2- allows us to infer the influence of the solvent on the electronic structure of the complex. Furthermore, the robust characterization of the dynamics and optical spectral signatures of the isolated 3MC intermediate provides a strong foundation for identifying 3MC intermediates in the electronic excited state relaxation mechanisms of similar Fe-centered systems being developed for solar applications.
|
|
| 21. |
- Laursen, Anne Cathrine Lund, et al.
(författare)
-
Trisomy 8 in pediatric acute myeloid leukemia : A NOPHO-AML study
- 2016
-
Ingår i: Genes, Chromosomes and Cancer. - : Wiley. - 1045-2257 .- 1098-2264. ; 55:9, s. 719-726
-
Tidskriftsartikel (refereegranskat)abstract
- Trisomy 8 (+8) is a common cytogenetic aberration in acute myeloid leukemia (AML); however, the impact of +8 in pediatric AML is largely unknown. We retrospectively investigated 609 patients from the NOPHO-AML database to determine the clinical and cytogenetic characteristics of +8 in pediatric AML and to investigate its prognostic impact. Complete cytogenetic data were available in 596 patients (98%) aged 0-18 years, diagnosed from 1993 to 2012, and treated according to the NOPHO-AML 1993 and 2004 protocols in the Nordic countries and Hong Kong. We identified 86 patients (14%) with +8. Trisomy 8 was combined with other cytogenetic aberrations in 68 patients (11%) (+8 other) and in 18 patients (3%), it was the sole abnormality (+8 alone). Trisomy 8 was associated with FAB M5 (36%) but otherwise clinically comparable with non-trisomy 8 patients. Trisomy 8 was favorable in patients of young age and with t(9;11). Trisomy 8 alone was associated with older age (median age 10.1 years), FAB M2 (33%), and FLT3-ITD mutations (58%). The 5-year event-free survival for patients with +8 alone was 50% and 5-year overall survival was 75%. In conclusion, +8 is one of the most common cytogenetic aberrations in pediatric AML. Trisomy 8 positive AML is a heterogeneous group and the majority of cases have additional cytogenetic aberrations. Patients with +8 alone differed from patients with +8 other and were associated with older age, FAB M2, and FLT3-ITD aberrations. There were no differences in survival despite the more frequent occurrence of FLT3-ITD in +8 alone.
|
|
| 22. |
- Laursen, Peter
(författare)
-
Documentation for the intergalactic radiative transfer code IGMtransfer
- 2010
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This document describes the publically available numerical code "IGMtransfer", capable of performing intergalactic radiative transfer (RT) of light in the vicinity of the Lyman alpha (Lya) line. Calculating the RT in a (possibly adaptively refined) grid of cells resulting from a cosmological simulation, the code returns 1) a "transmission function", showing how the intergalactic medium (IGM) affects the Lya line at a given redshift, and 2) the "average transmission" of the IGM, making it useful for studying the results of reionization simulations.
|
|
| 23. |
- Laursen, Peter, 1975-, et al.
(författare)
-
Intergalactic Transmission and its Impact on the Ly{\alpha} Line
- 2011
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 728:1, s. 52-
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- We study the intergalactic transmission of radiation in the vicinity of the Ly{\alpha} wavelength. Simulating sightlines through the intergalactic medium (IGM) in detailed cosmological hydrosimulations, the impact of the IGM on the shape of the line profile from Ly{\alpha} emitting galaxies at redshifts 2.5 to 6.5 is investigated. In particular we show that taking into account the correlation of the density and velocity fields of the IGM with the galaxies, the blue part of the spectrum may be appreciably reduced, even at relatively low redshifts. This may in some cases provide an alternative to the often-invoked outflow scenario, although it is concluded that this model is still a plausible explanation of the many asymmetric Ly{\alpha} profiles observed. Applying the calculated wavelength dependent transmission to simulated spectra from Ly{\alpha} emitting galaxies, we derive the fraction of photons that are lost in the IGM, in addition to what is absorbed internally in the galaxies due to dust. Moreover, by comparing the calculated transmission of radiation blueward of the Ly{\alpha} line, the total optical depth to Thomson scattering of cosmic microwave background, with corresponding observations, we are able to constrain the epoch when the Universe was reionized to z <~ 8.5.
|
|
| 24. |
- Laursen, Peter, 1975-
(författare)
-
Lyman α radiative transfer in the high-redshift, dusty Universe
- 2010
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The significance of the Ly{\alpha} emission line as a probe of the high-redshift Universe has long been established. Originating mainly in the vicinity of young, massive stars and in association with accretion of large bulks of matter, it is ideal for detecting young galaxies, the fundamental building blocks of our Universe. Since many different processes shape the spectrum and the spatial distribution of the Ly{\alpha} photons in various ways, a multitude of physical properties of galaxies can be unveiled. However, this also makes the interpretation of Ly{\alpha} observations notoriously difficult. Because Ly{\alpha} is a resonant line, it scatters on neutral hydrogen, having its path length from the source to our telescopes vastly increased, and taking it through regions of unknown physical conditions. In this work, a numerical code capable of calculating realistically the radiative transfer of Ly{\alpha} is presented. The code is capable of performing the radiative transfer in an arbitrary and adaptively refined distribution of Ly{\alpha} source emission, temperature and velocity field of the interstellar and intergalactic medium, as well as density of neutral and ionized hydrogen, and, particularly important, dust. Accordingly, it is applied to galaxies simulated at high resolution, yielding a number of novel and interesting results, most notably the escape fractions of Ly{\alpha} photons, the effect of dust on the line profile, and the impact of the transfer through the intergalactic medium. Furthermore, the remarkable detection of Ly{\alpha} emission from a so-called "damped Ly{\alpha} absorber" --- a special type of objects thought to be the progenitor of present-day's galaxies --- is presented, and the potential of the code for interpreting observations is demonstrated.
|
|
| 25. |
- Laursen, Peter, et al.
(författare)
-
ON THE (NON-) ENHANCEMENT OF THE Ly alpha EQUIVALENT WIDTH BY A MULTIPHASE INTERSTELLAR MEDIUM
- 2013
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 766:2, s. 124-
-
Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that radiative transfer effects may explain the unusually high equivalent widths (EWs) of the Ly alpha line, observed occasionally from starburst galaxies, especially at high redshifts. If the dust is locked up inside high-density clouds dispersed in an empty intercloud medium, the Ly alpha photons could scatter off of the surfaces of the clouds, effectively having their journey confined to the dustless medium. The continuum radiation, on the other hand, does not scatter, and would thus be subject to absorption inside the clouds. This scenario is routinely invoked when Ly alpha EWs higher than what is expected theoretically are observed, although the ideal conditions under which the results are derived usually are not considered. Here we systematically examine the relevant physical parameters in this idealized framework, testing whether any astrophysically realistic scenarios may lead to such an effect. It is found that although clumpiness indeed facilitates the escape of Ly alpha, it is highly unlikely that any real interstellar media should result in a preferential escape of Ly alpha over continuum radiation. Other possible causes are discussed, and it is concluded that the observed high EWs are more likely to be caused by cooling radiation from cold accretion and/or anisotropic escape of the Ly alpha radiation.
|
|
| 26. |
- Marion, Donna, et al.
(författare)
-
Predicting Life Satisfaction During Middle Adulthood from Peer Relationships During Mid-Adolescence
- 2013
-
Ingår i: Journal of Youth and Adolescence. - : Springer Science and Business Media LLC. - 0047-2891 .- 1573-6601. ; 42:8, s. 1299-1307
-
Tidskriftsartikel (refereegranskat)abstract
- The immediate advantages of adolescent friendships and disadvantages of peer rejection are well documented, but there is little evidence that these effects extend into adulthood. This study tested the hypothesis that peer relationships during adolescence predict life satisfaction during middle adulthood, using data from a 30-year prospective longitudinal study. Participants included 996 (49.5 % female) 8th grade students from a community sample of Swedish youth. Self-reports of friendship and peer reports of rejection were obtained when participants were age 15. Self-reports of global life satisfaction and perceived relationship quality were collected at age 43 for women and age 48 for men. Path analyses tested a direct-effects model that examined links from adolescent friendship participation and peer rejection to middle adulthood outcomes, and a buffered-effects model that examined links from adolescent peer rejection to middle adulthood outcomes, separately for those with and without friends during adolescence. Strong support emerged for the buffered-effects model but not the direct-effects model. Adolescent friendship participation moderated associations between adolescent peer rejection and adult global life satisfaction and between adolescent peer rejection and adult perceived relationship quality such that peer rejection predicted poorer adult outcomes for youth without friends but not for youth with friends. The findings suggest that the risks of peer rejection-and benefits of friendship-extend from adolescence well into middle age.
|
|
| 27. |
- Melinder, Jens, et al.
(författare)
-
Lyman alpha escape from 45 star forming galaxies– the Lyα Reference Sample XIV
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We present Lyα imaging of 45 low redshift star-forming galaxies observed with the Hubble space telescope. The galaxies have been selected to have moderate to high star formation rates using FUVluminosity and Hα equivalent width criteria, but no constraints on Lyα luminosity have been applied. We employ a pixel SED fitting code to obtain accurate continuum subtracted Lyα, Hα and Hβ maps. We find that Lyα is less concentrated than FUV and optical line emission in almost all galaxies with significant Lyα emission. We present global measurements of Lyα and other quantities measured in apertures designed to capture all of the Lyα emission. We then show how the escape fraction ofLyα relates to a number of other measured quantities (mass, metallicity, star formation, ionization parameter, and extinction). We find that the escape fraction is strongly anti-correlated with both nebular and stellar extinction, weakly anti-correlated with stellar mass, but no conclusive evidence for correlations to other quantities. We show that Lyα escape fractions are inconsistent with common dust extinction laws and discuss how a combination of radiative transfer effects and clumpy dust models can help resolve the discrepancies. We present a star formation rate calibration based on Lyαluminosity, where the equivalent width of Lyα is used to correct for non-unity escape fraction, and show that this relation provides a reasonably accurate calibration but with a large scatter. We also show stacked growth curves of Lyα for the galaxies that can be used to find aperture loss fractions at a given physical radius
|
|
| 28. |
- Melinder, Jens, 1977-, et al.
(författare)
-
The Lyα Reference Sample. XIV. Lyα Imaging of 45 Low-redshift Star-forming Galaxies and Inferences on Global Emission
- 2023
-
Ingår i: Astrophysical Journal Supplement Series. - 0067-0049 .- 1538-4365. ; 266:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present Lyα imaging of 45 low-redshift star-forming galaxies observed with the Hubble Space Telescope. The galaxies have been selected to have moderate to high star formation rates (SFRs) using far-ultraviolet (FUV) luminosity and Hα equivalent width criteria, but no constraints on Lyα luminosity. We employ a pixel stellar continuum fitting code to obtain accurate continuum-subtracted Lyα, Hα, and Hβ maps. We find that Lyα is less concentrated than FUV and optical line emission in almost all galaxies with significant Lyα emission. We present global measurements of Lyα and other quantities measured in apertures designed to capture all of the Lyα emission. We then show how the escape fraction of Lyα relates to a number of other measured quantities (mass, metallicity, star formation, ionization parameter, and extinction). We find that the escape fraction is strongly anticorrelated with nebular and stellar extinction, weakly anticorrelated with stellar mass, but no conclusive evidence for correlations with other quantities. We show that Lyα escape fractions are inconsistent with common dust extinction laws, and discuss how a combination of radiative transfer effects and clumpy dust models can help resolve the discrepancies. We present an SFR calibration based on Lyα luminosity, where the equivalent width of Lyα is used to correct for nonunity escape fraction, and show that this relation provides a reasonably accurate SFR estimate. We also show stacked growth curves of Lyα for the galaxies that can be used to find aperture loss fractions at a given physical radius.
|
|
| 29. |
- Nilsson, Kim, et al.
(författare)
-
Evolution in the properties of Lyman-alpha emitters from redshifts z ~ 3 to z ~ 2
- 2008
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Narrow-band surveys for Ly-alpha emitters (LAEs) is a powerful tool in detecting high, and very high, redshift galaxies. Even though samples are growing at redshifts z = 3 - 6, the nature of these galaxies is still poorly known. Aims: To study the properties of z = 2.25 LAEs and compare those with the properties of z > 3 LAEs. Methods: We present narrow-band imaging made with the MPG/ESO 2.2m telescope with the WFI detector. We have made a selection for emission-line objects and find 170 candidate typical LAEs and 17 candidates which we regard as high UV-transmission LAEs. We have derived the magnitudes of these objects in 8 bands from u* to Ks, and studied if they have X-ray and/or radio counterparts. Results: We show that there has been significant evolution in the properties of LAEs between redshift z ~ 3 and z = 2.25. The spread in spectral energy distributions (SEDs) at the lower redshift is larger and we detect a significant AGN contribution in the sample. The distribution of the equivalent widths is narrower than at z ~ 3, with only a few candidates with rest-frame equivalent width above the predicted limit of 240 A. The star formation rates derived from the Ly-alpha emission compared to that derived from the UV emission are lower by on average a factor of ~ 1.8, indicating a large absorption of dust. Conclusion: LAEs at redshift z = 2.25 may be more evolved than LAEs at higher redshift. The red SEDs imply more massive, older and/or more dusty galaxies at lower redshift than observed at higher redshifts. The decrease in equivalent widths and star formation rates indicate more quiescent galaxies, with in general less star formation than in higher redshift galaxies. At z = 2.25, AGN appear to be more abundant and also to contribute more to the LAE population.
|
|
| 30. |
- Noterdaeme, P., et al.
(författare)
-
Discovery of a compact gas-rich damped Lyman-alpha galaxy at z = 2.2 : evidence of a starburst driven outflow
- 2012
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 540, s. A63-
-
Tidskriftsartikel (refereegranskat)abstract
- We present the detection of Ly alpha, [OIII], and H alpha emission associated with an extremely strong damped Lyman-alpha (DLA) system (N(HI) = 10(22.10) cm(-2)) at z = 2.207 towards the quasar SDSS J113520.39-001053.56. This is the largest Hi column density ever measured along a quasi-stellar object (QSO) line of sight, though typical of those often found in DLAs associated to gamma-ray bursts (GRBs). This absorption system can also be classified as an ultra-strong Mg II system with W-r(lambda 2796) similar or equal to 3.6 angstrom. The mean metallicity of the gas ([Zn/H] = -1.1) and dust depletion factors ([Zn/Fe] = 0.72, [Zn/Cr] = 0.49) are consistent with (and only marginally larger than) the mean values found in the general QSO-DLA population. The [OIII]-H alpha emitting region has a very small impact parameter with respect to the QSO line of sight, b approximate to 0.1 '' (0.9 kpc proper distance), and is unresolved. From the H alpha line, we measure a significant star formation rate (SFR) approximate to 25 M-circle dot yr(-1) (uncorrected for dust). The shape of the Ly alpha line is double-peaked, which is the signature of a resonant scattering of Ly alpha photons, and the Ly alpha emission is spatially extended. More strikingly, the blue and red Ly alpha peaks arise from distinct regions extended over a few kpc on either side of the star-forming region. We propose that this is the consequence of a Ly alpha transfer in outflowing gas. The presence of starburst-driven outflows is also in agreement with the high SFR together with the small size and low mass of the galaxy (M-vir similar to 10(10) M-circle dot). By placing constraints on the stellar UV continuum luminosity of the galaxy, we estimate an age of at most a few 10(7) yr, again consistent with a recent starburst scenario. We interpret these data as the observation of a young, gas-rich, compact starburst galaxy, from which material is expelled through collimated winds powered by the vigorous star formation activity. We substantiate this picture by modelling the radiative transfer of Ly alpha photons in the galactic counterpart. Though our model (a spherical galaxy with bipolar outflowing jets) is a simplistic representation of the true gas distribution and velocity field, the agreement between the observed and simulated properties is particularly good (spectral shape and width of the Lyman-alpha emission, spatial configuration, escape fraction as well as absorption kinematics, HI column density, and dust reddening). Finally, we propose that selecting DLAs with very high Hi column densities may be an efficient way of detecting star-forming galaxies at small impact parameters from the background QSO lines of sight.
|
|
| 31. |
- Pardy, Stephen A., et al.
(författare)
-
THE LYMAN ALPHA REFERENCE SAMPLE. III. PROPERTIES OF THE NEUTRAL ISM FROM GBT AND VLA OBSERVATIONS
- 2014
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 794:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present new Hi imaging and spectroscopy of the 14 UV-selected star-forming galaxies in the Lyman Alpha Reference Sample (LARS), aimed for a detailed study of the processes governing the production, propagation, and escape of Ly alpha photons. New Hi spectroscopy, obtained with the 100 m Green Bank Telescope (GBT), robustly detects the Hi spectral line in 11 of the 14 observed LARS galaxies (although the profiles of two of the galaxies are likely confused by other sources within the GBT beam); the three highest redshift galaxies are not detected at our current sensitivity limits. The GBT profiles are used to derive fundamental Hi line properties of the LARS galaxies. We also present new pilot Hi spectral line imaging of five of the LARS galaxies obtained with the Karl G. Jansky Very Large Array (VLA). This imaging localizes the Hi gas and provides a measurement of the total Hi mass in each galaxy. In one system, LARS 03 (UGC 8335 or Arp 238), VLA observations reveal an enormous tidal structure that extends over 160 kpc from the main interacting systems and that contains >10(9) M-circle dot of Hi. We compare various Hi properties with global Ly alpha quantities derived from Hubble Space Telescope measurements. The measurements of the Ly alpha escape fraction are coupled with the new direct measurements of Hi mass and significantly disturbed Hi velocities. Our robustly detected sample reveals tentative correlations between the total Hi mass and linewidth, and key Ly alpha tracers. Further, on global scales, these data support a complex coupling between Ly alpha propagation and the Hi properties of the surrounding medium.
|
|
| 32. |
- Ranjan, A., et al.
(författare)
-
Molecular gas and star formation in an absorption-selected galaxy : Hitting the bull's eye at z similar or equal to 2.46
- 2018
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 618
-
Tidskriftsartikel (refereegranskat)abstract
- We present the detection and detailed analysis of a diffuse molecular cloud at z(abs) = 2.4636 towards the quasar SDSS J 1513+0352 (z(em) similar or equal to 2.68) observed with the X-shooter spectrograph at the Very Large Telescope. We measured very high column densities of atomic and molecular hydrogen with log N(H-I; H-2) similar or equal to 21.8; 21.3. This is the highest H-2 column density ever measured in an intervening damped Lyman-alpha system but we did not detect CO, implying log N(CO)/N(H-2) < -7.8, which could be due to a low metallicity of the cloud. From the metal absorption lines, we derived the metallicity to be Z similar or equal to 0.15 Z(circle dot) and determined the amount of dust by measuring the induced extinction of the background quasar light, A(V) similar or equal to 0.4. We simultaneously detected Lyman-alpha emission at the same redshift with a centroid located at a most probable impact parameter of only rho similar or equal to 1.4 kpc. We argue that the line of sight is therefore likely passing through the interstellar medium (ISM), as opposed to the circumgalactic medium (CGM), of a galaxy. The relation between the surface density of gas and that of star formation seems to follow the global empirical relation derived in the nearby Universe although our constraints on the star formation rate (SFR) and the galaxy extent remain too loose to be conclusive. We study the transition from atomic to molecular hydrogen using a theoretical description based on the microphysics of molecular hydrogen. We use the derived chemical properties of the cloud and physical conditions (T-k similar or equal to 90K and n similar or equal to 250 cm(3)) derived through the excitation of H-2 rotational levels and neutral carbon fine structure transitions to constrain the fundamental parameters that govern this transition. By comparing the theoretical and observed HI column densities, we are able to bring an independent constraint on the incident ultra-violet (UV) flux, which we find to be in agreement with that estimated from the observed SFR.
|
|
| 33. |
- Rivera-Thorsen, Thöger E., et al.
(författare)
-
THE LYMAN ALPHA REFERENCE SAMPLE. V. THE IMPACT OF NEUTRAL ISM KINEMATICS ANDGEOMETRY ON Lyα ESCAPE
- 2015
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 805:14
-
Tidskriftsartikel (refereegranskat)abstract
- We present high-resolution far-UV spectroscopy of the 14 galaxies of the Lyα Reference Sample; a sample of strongly star-forming galaxies at low redshifts (0.028 < z < 0.18). We compare the derived properties to global properties derived from multi-band imaging and 21 cm H i interferometry and single-dish observations, as well as archival optical SDSS spectra. Besides the Lyα line, the spectra contain a number of metal absorption features allowing us to probe the kinematics of the neutral ISM and evaluate the optical depth and and covering fraction of the neutral medium as a function of line of sight velocity. Furthermore, we show how this, in combination with the precise determination of systemic velocity and good Lyα spectra, can be used to distinguish a model in which separate clumps together fully cover the background source, from the "picket fence" model named by Heckman et al. We find that no one single effect dominates in governing Lyα radiative transfer and escape. Lyα escape in our sample coincides with a maximum velocity-binned covering fraction of 0.9 and bulk outflow velocities of 50 km s−1, although a number of galaxies show these characteristics and yet little or no Lyα escape. We find that Lyα peak velocities, where available, are not consistent with a strong backscattered component, but rather with a simpler model of an intrinsic emission line overlaid by a blueshifted absorption profile from the outflowing wind. Finally, we find a strong anticorrelation between Hα equivalent width and maximum velocity-binned covering factor, and propose a heuristic explanatory model.
|
|
| 34. |
|
|
| 35. |
- Sollerman, J., et al.
(författare)
-
Supernova 2006aj and the associated X-Ray Flash 060218
- 2006
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 454, s. 503-509
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the afterglow of the gamma-ray burst (GRB) of February 18, 2006. This is a nearby long GRB, with a very low peak energy, and is therefore classified as an X-ray Flash (XRF). XRF 060218 is clearly associated with a supernova - dubbed SN 2006aj. We present early spectra for SN 2006aj as well as optical lightcurves reaching out to 50 days past explosion. Our optical lightcurves define the rise times, the lightcurve shapes and the absolute magnitudes in the U, V and R bands, and we compare these data with data for other relevant supernovae. SN 2006aj evolved quite fast, somewhat similarly to SN 2002ap, but not as fast as SN 1994I. Our spectra show the evolution of the supernova over the peak, when the U-band portion of the spectrum rapidly fades due to extensive line blanketing. We compare to similar spectra of very energetic type Ic supernovae. Our first spectra are earlier than spectra for any other GRB-SN. The spectrum taken 12 days after burst in the rest frame is similar to somewhat later spectra of both SN 1998bw and SN 2003dh, implying a rapid early evolution. This is consistent with the fast lightcurve. From the narrow emission lines from the host galaxy we derive a redshift of z=0.0331±0.0007. This makes XRF 060218 the second closest gamma-ray burst detected. The flux of these emission lines indicate a high-excitation state, and a modest metallicity and star formation rate of the host galaxy.
|
|
| 36. |
- Taneja, Pankaj, et al.
(författare)
-
Reliability of orofacial quantitative sensory testing for pleasantness and unpleasantness
- 2020
-
Ingår i: Cephalalgia. - : Sage Publications. - 0333-1024 .- 1468-2982. ; 40:11
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Quantitative sensory testing protocols for perceptions of pleasantness and unpleasantness based on the German Research Network on Neuropathic Pain protocol were recently introduced. However, there are no reliability studies yet published.AIM: To evaluate the intra-examiner (test-retest) and inter-examiner reliability for orofacial pleasantness and unpleasantness quantitative sensory testing protocols.METHODS: Sixteen healthy participants from Aarhus University (11 women and five men, mean age 24, range 21-26 years) contributed. Two examiners were trained in performing the entire quantitative sensory testing protocols for pleasantness and unpleasantness, which included the additional dynamic tactile stimulation test using a goat-hair brush. Each participant underwent examination of both protocols by each examiner (inter-examiner reliability) on day 1. They returned at least 8 days following the testing to be re-examined by one examiner (intra-examiner reliability). All testing was performed on the skin of the right mandibular mental region. The intraclass correlation (ICC) was used to determine reliability.RESULTS: For the protocol investigating pleasantness, the majority of parameters had good to excellent intra-examiner (11/14: Intraclass correlation 0.67-0.87) and inter-examiner (13/14: Intraclass correlation 0.62-0.96) reliabilities. Similarly, the protocol investigating unpleasantness had good to excellent intra-examiner (intraclass correlation 0.63-0.99) and inter-examiner (intraclass correlation 0.65-0.98) reliabilities for most (13/15) of the parameters.CONCLUSION:Intra and inter-examiner reliabilities in the majority of quantitative sensory testing parameters (apart from the summation ratio) investigating pleasantness and unpleasantness are acceptable when assessing somatosensory function of the orofacial region.Trial registration: NA.
|
|
| 37. |
- Tatsuno, Hideyuki, et al.
(författare)
-
Hot Branching Dynamics in a Light-Harvesting Iron Carbene Complex Revealed by Ultrafast X-ray Emission Spectroscopy
- 2020
-
Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 59:1, s. 364-372
-
Tidskriftsartikel (refereegranskat)abstract
- Iron N-heterocyclic carbene (NHC) complexes have received a great deal of attention recently because of their growing potential as light sensitizers or photocatalysts. We present a sub-ps X-ray spectroscopy study of an FeIINHC complex that identifies and quantifies the states involved in the deactivation cascade after light absorption. Excited molecules relax back to the ground state along two pathways: After population of a hot 3MLCT state, from the initially excited 1MLCT state, 30 % of the molecules undergo ultrafast (150 fs) relaxation to the 3MC state, in competition with vibrational relaxation and cooling to the relaxed 3MLCT state. The relaxed 3MLCT state then decays much more slowly (7.6 ps) to the 3MC state. The 3MC state is rapidly (2.2 ps) deactivated to the ground state. The 5MC state is not involved in the deactivation pathway. The ultrafast partial deactivation of the 3MLCT state constitutes a loss channel from the point of view of photochemical efficiency and highlights the necessity to screen transition-metal complexes for similar ultrafast decays to optimize photochemical performance.
|
|
| 38. |
- Valenti, S., et al.
(författare)
-
The Carbon-rich Type Ic SN 2007gr : The Photospheric Phase
- 2008
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 673:2, s. L155-L158
-
Tidskriftsartikel (refereegranskat)abstract
- The first 2 months of spectroscopic and photometric monitoring of the nearby Type Ic SN 2007gr are presented. The very early discovery (less than 5 days after the explosion) and the relatively short distance of the host galaxy motivated an extensive observational campaign. SN 2007gr shows an average peak luminosity but unusually narrow spectral lines and an almost flat photospheric velocity profile. The detection of prominent carbon features in the spectra is shown and suggests a wide range in carbon abundance in stripped-envelope supernovae. SN 2007gr may be an important piece in the puzzle of the observed diversity of CC SNe.
|
|
| 39. |
- Watson, Darach, et al.
(författare)
-
HELIUM IN NATAL H II REGIONS : THE ORIGIN OF THE X-RAY ABSORPTION IN GAMMA-RAY BURST AFTERGLOWS
- 2013
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 768:1, s. 23-
-
Tidskriftsartikel (refereegranskat)abstract
- Soft X-ray absorption in excess of Galactic is observed in the afterglows of most gamma-ray bursts (GRBs), but the correct solution to its origin has not been arrived at after more than a decade of work, preventing its use as a powerful diagnostic tool. We resolve this long-standing problem and find that absorption by He in the GRB's host H II region is responsible for most of the absorption. We show that the X-ray absorbing column density (N-HX) is correlated with both the neutral gas column density and with the optical afterg(l)ow's dust extinction (A(V)). This correlation explains the connection between dark bursts and bursts with high N-HX values. From these correlations, we exclude an origin of the X-ray absorption which is not related to the host galaxy, i.e., the intergalactic medium or intervening absorbers are not responsible. We find that the correlation with the dust column has a strong redshift evolution, whereas the correlation with the neutral gas does not. From this, we conclude that the column density of the X-ray absorption is correlated with the total gas column density in the host galaxy rather than the metal column density, in spite of the fact that X-ray absorption is typically dominated by metals. The strong redshift evolution of N-HX/A(V) is thus a reflection of the cosmic metallicity evolution of star-forming galaxies and we find it to be consistent with measurements of the redshift evolution of metallicities for GRB host galaxies. We conclude that the absorption of X-rays in GRB afterglows is caused by He in the H II region hosting the GRB. While dust is destroyed and metals are stripped of all of their electrons by the GRB to great distances, the abundance of He saturates the He-ionizing UV continuum much closer to the GRB, allowing it to remain in the neutral or singly-ionized state. Helium X-ray absorption explains the correlation with total gas, the lack of strong evolution with redshift, as well as the absence of dust, metal or hydrogen absorption features in the optical-UV spectra.
|
|
| 40. |
- Watson, D., et al.
(författare)
-
The metallicity of gamma-ray burst environments from high-energy observations
- 2011
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 527, s. A104-
-
Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray bursts (GRBs) and their early afterglows ionise their circumburst material. Only high-energy spectroscopy therefore, allows examination of matter close to the burst itself. Soft X-ray absorption allows an estimate to be made of the total column density in metals. The detection of the X-ray afterglow can also be used to place a limit on the total gas column along the line of sight based on the Compton scattering opacity. Such a limit would enable, for the first time, the determination of lower limits on the metallicity in the circumburst environments of GRBs. In this paper, we determine the limits that can be placed on the total gas column density in the vicinities of GRBs based on Compton scattering. We simulate the effects of Compton scattering on a collimated beam of high-energy photons passing through a shell of high column-density material to determine the expected lightcurves, luminosities, and spectra. We compare these predictions to observations, and determine what limits can be placed on the total gas column density. The smearing out of pulses in the lightcurve from Compton scattering is not likely to be observable, and its absence does not place strong constraints on the Compton depth. However, the distribution of observed luminosities of bursts allows us to place statistical, model-dependent limits that are typically less than or similar to 10(25) cm(-2) for less luminous bursts, and as low as similar to 10(24) cm(-2) for the most luminous. By using the shape of the high-energy broadband spectrum, however, limits as low as similar to 5 x 10(24) cm(-2) can be placed on individual bursts, implying metallicity lower limits from X-and gamma-rays alone from 0 up to 0.01 Z/Z(circle dot). At extremely high redshifts, this limit would be at least 0.02 Z/Z(circle dot), enough to distinguish population III from non-primordial GRBs.
|
|
| 41. |
- Watson, D., et al.
(författare)
-
The metallicity of gamma-ray burst environments from high energy observations
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746.
-
Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray bursts (GRBs) and their early afterglows ionise their circumburst material. Only high-energy spectroscopy therefore, allows examination of the matter close to the burst itself. Soft X-ray absorption allows an estimate to be made of the total column density in metals. The detection of the X-ray afterglow can also be used to place a limit on the total gas column along the line of sight based on the Compton scattering opacity. Such a limit would enable, for the first time, the determination of lower limits on the metallicity in the circumburst environments of GRBs. In this paper, we determine the limits that can be placed on the total gas column density in the vicinities of GRBs based on the Compton scattering. We simulate the effects of Compton scattering on a collimated beam of high energy photons passing through a shell of high column density material to determine the expected lightcurves, luminosities, and spectra. We compare these predictions to observations, and determine what limits can realistically be placed on the total gas column density. The smearing out of pulses in the lightcurve from Compton scattering is not likely to be observable, and its absence does not place strong constraints on the Compton depth for GRBs. However, the distribution of observed luminosities of bursts allows us to place statistical, model-dependent limits that are typically <~1e25 cm^{-2} for less luminous bursts, and as low as ~1e24 cm$^{-2} for the most luminous. Using the shape of the high-energy broadband spectrum, however, in some favourable cases, limits as low as ~5e24 cm^{-2} can placed on individual bursts, implying metallicity lower limits from X- and gamma-rays alone from 0 up to 0.01 Z/Zsun. At extremely high redshifts, this limit would be at least 0.02 Z/Z_sun, enough to discriminate population III from non-primordial GRBs.
|
|
| 42. |
- Östlin, Göran, et al.
(författare)
-
THE Ly alpha REFERENCE SAMPLE. I. SURVEY OUTLINE AND FIRST RESULTS FOR MARKARIAN 259
- 2014
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 797:1
-
Tidskriftsartikel (refereegranskat)abstract
- The Ly alpha Reference Sample (LARS) is a substantial program with the Hubble Space Telescope (HST) that provides a sample of local universe laboratory galaxies in which to study the detailed astrophysics of the visibility and strength of the Ly alpha line of neutral hydrogen. Ly alpha is the dominant spectral line in use for characterizing high-redshift (z) galaxies. This paper presents an overview of the survey, its selection function, and HST imaging observations. The sample was selected from the combined GALEX+Sloan Digital Sky Survey catalog at z = 0.028-0.19, in order to allow Ly alpha to be captured with combinations of long-pass filters in the Solar Blind Channel (SBC) of the Advanced Camera for Surveys (ACS) onboard HST. In addition, LARS utilizes H alpha and H beta narrowband and u, b, i broadband imaging with ACS and the Wide Field Camera 3 (WFC3). In order to study galaxies in which large numbers of Ly alpha photons are produced (whether or not they escape), we demanded an H alpha equivalent width W(H alpha) >= 100 angstrom. The final sample of 14 galaxies covers far-UV (FUV, lambda similar to 1500 angstrom) luminosities that overlap with those of high-z Ly alpha emitters (LAEs) and Lyman break galaxies (LBGs), making LARS a valid comparison sample. We present the reduction steps used to obtain the Ly alpha images, including our LARS eXtraction software (LaXs), which utilizes pixel-by-pixel spectral synthesis fitting of the energy distribution to determine and subtract the continuum at Ly alpha. We demonstrate that the use of SBC long-pass-filter combinations increase the signal-to-noise ratio by an order of magnitude compared to the nominal Ly alpha filter available in SBC. To exemplify the science potential of LARS, we also present some first results for a single galaxy, Mrk 259 (LARS #1). This irregular galaxy shows bright and extended (indicative of resonance scattering) but strongly asymmetric Ly alpha emission. Spectroscopy from the Cosmic Origins Spectrograph on board HST centered on the brightest UV knot shows a moderate outflow in the neutral interstellar medium (probed by low ionization stage absorption features) and Ly alpha emission with an asymmetric profile. Radiative transfer modeling is able to reproduce the essential features of the Ly alpha line profile and confirms the presence of an outflow. From the integrated photometry we measure an Ly alpha luminosity of L-Ly alpha= 1.3x10(42) erg s(-1) an equivalent width W(Ly alpha) = 45 angstrom and an FUV absolute magnitude M-FUV = -19.2 (AB). Mrk 259 would hence be detectable in high-z Ly alpha and LBG surveys. The total Ly alpha escape fraction is 12%. This number is higher than the low-z average, but similar to that at z > 4, demonstrating that LARS provides a valid comparison sample for high-z galaxy studies.
|
|
| 43. |
- Östlin, Göran, et al.
(författare)
-
The Source of Leaking Ionizing Photons from Haro11 : Clues from HST/COS Spectroscopy of Knots A, B, and C
- 2021
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 912:2
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the escape of ionizing (Lyman continuum) photons from galaxies is vital for determining how galaxies contributed to reionization in the early universe. While directly detecting the Lyman continuum from high-redshift galaxies is impossible due to the intergalactic medium, low-redshift galaxies in principle offer this possibility but require observations from space. The first local galaxy for which Lyman continuum escape was found is Haro 11, a luminous blue compact galaxy at z = 0.02, where observations with the FUSE satellite revealed an escape fraction of 3.3%. However, the FUSE aperture covers the entire galaxy, and it is not clear from where the Lyman continuum is leaking out. Here we utilize Hubble Space Telescope/Cosmic Origins Spectrograph spectroscopy in the wavelength range 1100-1700 angstrom of the three knots (A, B, and C) of Haro 11 to study the presence of Ly alpha emission and the properties of intervening gas. We find that all knots have bright Ly alpha emission. UV absorption lines, originating in the neutral interstellar medium, as well as lines probing the ionized medium, are seen extending to blueshifted velocities of 500 km s(-1) in all three knots, demonstrating the presence of an outflowing multiphase medium. We find that knots A and B have large covering fractions of neutral gas, making LyC escape along these sightlines improbable, while knot C has a much lower covering fraction (less than or similar to 50%). Knot C also has the the highest Ly alpha escape fraction, and we conclude that it is the most likely source of the escaping Lyman continuum detected in Haro 11.
|
|
