| 1. |
|
|
| 2. |
- Loisel, J., et al.
(författare)
-
Expert assessment of future vulnerability of the global peatland carbon sink
- 2021
-
Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 11:1, s. 70-77
-
Tidskriftsartikel (refereegranskat)abstract
- Peatlands are impacted by climate and land-use changes, with feedback to warming by acting as either sources or sinks of carbon. Expert elicitation combined with literature review reveals key drivers of change that alter peatland carbon dynamics, with implications for improving models. The carbon balance of peatlands is predicted to shift from a sink to a source this century. However, peatland ecosystems are still omitted from the main Earth system models that are used for future climate change projections, and they are not considered in integrated assessment models that are used in impact and mitigation studies. By using evidence synthesized from the literature and an expert elicitation, we define and quantify the leading drivers of change that have impacted peatland carbon stocks during the Holocene and predict their effect during this century and in the far future. We also identify uncertainties and knowledge gaps in the scientific community and provide insight towards better integration of peatlands into modelling frameworks. Given the importance of the contribution by peatlands to the global carbon cycle, this study shows that peatland science is a critical research area and that we still have a long way to go to fully understand the peatland-carbon-climate nexus.
|
|
| 3. |
- Bansal, Sheel, et al.
(författare)
-
Practical Guide to Measuring Wetland Carbon Pools and Fluxes
- 2023
-
Ingår i: Wetlands (Wilmington, N.C.). - : SPRINGER. - 0277-5212 .- 1943-6246. ; 43:8
-
Forskningsöversikt (refereegranskat)abstract
- Wetlands cover a small portion of the world, but have disproportionate influence on global carbon (C) sequestration, carbon dioxide and methane emissions, and aquatic C fluxes. However, the underlying biogeochemical processes that affect wetland C pools and fluxes are complex and dynamic, making measurements of wetland C challenging. Over decades of research, many observational, experimental, and analytical approaches have been developed to understand and quantify pools and fluxes of wetland C. Sampling approaches range in their representation of wetland C from short to long timeframes and local to landscape spatial scales. This review summarizes common and cutting-edge methodological approaches for quantifying wetland C pools and fluxes. We first define each of the major C pools and fluxes and provide rationale for their importance to wetland C dynamics. For each approach, we clarify what component of wetland C is measured and its spatial and temporal representativeness and constraints. We describe practical considerations for each approach, such as where and when an approach is typically used, who can conduct the measurements (expertise, training requirements), and how approaches are conducted, including considerations on equipment complexity and costs. Finally, we review key covariates and ancillary measurements that enhance the interpretation of findings and facilitate model development. The protocols that we describe to measure soil, water, vegetation, and gases are also relevant for related disciplines such as ecology. Improved quality and consistency of data collection and reporting across studies will help reduce global uncertainties and develop management strategies to use wetlands as nature-based climate solutions.
|
|
| 4. |
- Zavala, J. A., et al.
(författare)
-
The Evolution of the IR Luminosity Function and Dust-obscured Star Formation over the Past 13 Billion Years
- 2021
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 909:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present the first results from the Mapping Obscuration to Reionization with ALMA (MORA) survey, the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous survey to date (184 arcmin(2)) and the only at 2 mm to search for dusty star-forming galaxies (DSFGs). We use the 13 sources detected above 5 sigma to estimate the first ALMA galaxy number counts at this wavelength. These number counts are then combined with the state-of-the-art galaxy number counts at 1.2 and 3 mm and with a backward evolution model to place constraints on the evolution of the IR luminosity function and dust-obscured star formation in the past 13 billion years. Our results suggest a steep redshift evolution on the space density of DSFGs and confirm the flattening of the IR luminosity function at faint luminosities, with a slope of alpha(LF) = -0.42(-0.04)(+0.02). We conclude that the dust-obscured component, which peaks at z approximate to 2-2.5, has dominated the cosmic history of star formation for the past similar to 12 billion years, back to z similar to 4. At z = 5, the dust-obscured star formation is estimated to be similar to 35% of the total star formation rate density and decreases to 25%-20% at z = 6-7, implying a minor contribution of dusten-shrouded star formation in the first billion years of the universe. With the dust-obscured star formation history constrained up to the end of the epoch of reionization, our results provide a benchmark to test galaxy formation models, to study the galaxy mass assembly history, and to understand the dust and metal enrichment of the universe at early times.
|
|
| 5. |
- Boukhvalov D. W., Kurmaev E. Z. , Moewes A. , Zatsepin D. A., Cherkashenko V. M., Nemnonov S. N., Finkelstein L. D. , Yarmoshenko Yu. M., Neumann M., Dobrovitski V. V. , Katsnelson M. I. , Lichtenstein A. I. , Harmon B. N. , Kögerler P.
(författare)
-
Electronic structure of magnetic molecules V15: LSDA+U calculations, X-ray emission and photoelectron spectra
- 2003
-
Ingår i: Physical Review B. ; 67, s. 134408-
-
Tidskriftsartikel (refereegranskat)
|
|
| 6. |
- Fischer, Hubertus, et al.
(författare)
-
Palaeoclimate constraints on the impact of 2 °C anthropogenic warming and beyond
- 2018
-
Ingår i: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 11:7, s. 474-485
-
Tidskriftsartikel (refereegranskat)abstract
- Over the past 3.5 million years, there have been several intervals when climate conditions were warmer than during the pre-industrial Holocene. Although past intervals of warming were forced differently than future anthropogenic change, such periods can provide insights into potential future climate impacts and ecosystem feedbacks, especially over centennial-to-millennial timescales that are often not covered by climate model simulations. Our observation-based synthesis of the understanding of past intervals with temperatures within the range of projected future warming suggests that there is a low risk of runaway greenhouse gas feedbacks for global warming of no more than 2 °C. However, substantial regional environmental impacts can occur. A global average warming of 1–2 °C with strong polar amplification has, in the past, been accompanied by significant shifts in climate zones and the spatial distribution of land and ocean ecosystems. Sustained warming at this level has also led to substantial reductions of the Greenland and Antarctic ice sheets, with sea-level increases of at least several metres on millennial timescales. Comparison of palaeo observations with climate model results suggests that, due to the lack of certain feedback processes, model-based climate projections may underestimate long-term warming in response to future radiative forcing by as much as a factor of two, and thus may also underestimate centennial-to-millennial-scale sea-level rise.
|
|
| 7. |
- Laurell, H., et al.
(författare)
-
Continuous-variable quantum state tomography of photoelectrons
- 2022
-
Ingår i: Physical Review Research. - 2643-1564. ; 4:3
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a continuous variable quantum state tomography protocol of electrons which result from the ionization of atoms or molecules by the absorption of extreme ultraviolet light pulses. Our protocol is benchmarked against a direct calculation of the quantum state of photoelectrons ejected from helium and argon in the vicinity of a Fano resonance. In the latter case, we furthermore distill ion-photoelectron entanglement due to spin-orbit splitting. This opens routes toward the investigation of quantum coherence and entanglement properties on the ultrafast timescale.
|
|
| 8. |
- Windhorst, Rogier A., et al.
(författare)
-
JWST PEARLS. Prime extragalactic areas for reionization and lensing science : project overview and first results
- 2023
-
Ingår i: Astronomical Journal. - : Institute of Physics (IOP). - 0004-6256 .- 1538-3881. ; 165:1
-
Tidskriftsartikel (refereegranskat)abstract
- We give an overview and describe the rationale, methods, and first results from NIRCam images of the JWST “Prime Extragalactic Areas for Reionization and Lensing Science” (PEARLS) project. PEARLS uses up to eight NIRCam filters to survey several prime extragalactic survey areas: two fields at the North Ecliptic Pole (NEP); seven gravitationally lensing clusters; two high redshift protoclusters; and the iconic backlit VV 191 galaxy system to map its dust attenuation. PEARLS also includes NIRISS spectra for one of the NEP fields and NIRSpec spectra of two high-redshift quasars. The main goal of PEARLS is to study the epoch of galaxy assembly, active galactic nucleus (AGN) growth, and First Light. Five fields—the JWST NEP Time-Domain Field (TDF), IRAC Dark Field, and three lensing clusters—will be observed in up to four epochs over a year. The cadence and sensitivity of the imaging data are ideally suited to find faint variable objects such as weak AGN, high-redshift supernovae, and cluster caustic transits. Both NEP fields have sightlines through our Galaxy, providing significant numbers of very faint brown dwarfs whose proper motions can be studied. Observations from the first spoke in the NEP TDF are public. This paper presents our first PEARLS observations, their NIRCam data reduction and analysis, our first object catalogs, the 0.9–4.5 μm galaxy counts and Integrated Galaxy Light. We assess the JWST sky brightness in 13 NIRCam filters, yielding our first constraints to diffuse light at 0.9–4.5 μm. PEARLS is designed to be of lasting benefit to the community.
|
|
| 9. |
- Boukhvalov, D. W., et al.
(författare)
-
Electronic structure of a Mn-12 molecular magnet : Theory and experiment
- 2007
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:1, s. 014419-
-
Tidskriftsartikel (refereegranskat)abstract
- We used site-selective and element-specific resonant inelastic x-ray scattering (RIXS) to study the electronic structure and the electron interaction effects in the molecular magnet [Mn12O12(CH3COO)(16)(H2O)(4)]center dot 2CH(3)COOH center dot 4H(2)O, and compared the experimental data with the results of local spin density approximation +U electron structure calculations which include the on-site Coulomb interactions. We found a good agreement between theory and experiment for the Coulomb repulsion parameter U = 4 eV. In particular, the p-d band separation of 1.8 eV has been found from the RIXS spectra, which is in accordance with the calculations. Similarly, the positions of the peaks in the XPS spectra agree with the calculated densities of p and d states. Using the results of the electronic structure calculations, we determined the intramolecular exchange parameters, and used them for diagonalization of the Mn-12 spin Hamiltonian. The calculated exchanges gave the correct ground state with the total spin S = 10.
|
|
| 10. |
|
|
| 11. |
- Casey, Caitlin M., et al.
(författare)
-
Physical Characterization of an Unlensed, Dusty Star-forming Galaxy at z = 5.85
- 2019
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 887:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present a physical characterization of MM J100026.36+021527.9 (a.k.a. "Mambo-9"), a dusty star-forming galaxy (DSFG) at z = 5.850 ± 0.001. This is the highest-redshift unlensed DSFG (and fourth most distant overall) found to date and is the first source identified in a new 2 mm blank-field map in the COSMOS field. Though identified in prior samples of DSFGs at 850 μm to 1.2 mm with unknown redshift, the detection at 2 mm prompted further follow-up as it indicated a much higher probability that the source was likely to sit at z > 4. Deep observations from the Atacama Large Millimeter and submillimeter Array (ALMA) presented here confirm the redshift through the secure detection of 12CO(J = 6→5) and p-H2O (21,1 → 20,2). Mambo-9 is composed of a pair of galaxies separated by 6 kpc with corresponding star formation rates of 590 M o˙ yr-1 and 220 M o˙ yr-1, total molecular hydrogen gas mass of (1.7 ± 0.4) × 1011 M o˙, dust mass of (1.3 ± 0.3) × 109 M o˙, and stellar mass of (3.2-1.5+1.0) × 109 M o˙. The total halo mass, (3.3 ± 0.8) × 1012 M o˙, is predicted to exceed 1015 M o˙ by z = 0. The system is undergoing a merger-driven starburst that will increase the stellar mass of the system tenfold in τ depl = 40-80 Myr, converting its large molecular gas reservoir (gas fraction of 96-2+1) into stars. Mambo-9 evaded firm spectroscopic identification for a decade, following a pattern that has emerged for some of the highest-redshift DSFGs found. And yet, the systematic identification of unlensed DSFGs like Mambo-9 is key to measuring the global contribution of obscured star formation to the star formation rate density at z ⪆ 4, the formation of the first massive galaxies, and the formation of interstellar dust at early times (≲1 Gyr).
|
|
| 12. |
|
|
| 13. |
- Chisholm, J., et al.
(författare)
-
The far-ultraviolet continuum slope as a Lyman Continuum escape estimator at high redshift
- 2022
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 517:4, s. 5104-5120
-
Tidskriftsartikel (refereegranskat)abstract
- Most of the hydrogen in the intergalactic medium (IGM) was rapidly ionized at high redshifts. While observations have established that reionization occurred, observational constraints on the high-redshift ionizing emissivity remain elusive. Here, we present a new analysis of the Low-redshift Lyman Continuum Survey (LzLCS) and literature observations, a combined sample of 89 star-forming galaxies at redshifts near 0.3 with Hubble Space Telescope observations of their ionizing continua (or Lyman Continuum, LyC). We find a strong (6σ significant) inverse correlation between the continuum slope at 1550 Å (defined as Fλ ∝ λβ1550obs) and both the LyC escape fraction (fesc, LyC) and fesc, LyC times the ionizing photon production efficiency (ξion). On average, galaxies with redder continuum slopes have smaller fesc, LyC than galaxies with bluer slopes mainly due to higher dust attenuation. More than 5 per cent (20 per cent) of the LyC emission escapes galaxies with β1550obs <−2.1 (−2.6). We find strong correlations between β1550obs and the [O III]/[O II] flux ratio (at 7.5σ significance), galaxy stellar mass (at 5.9σ), the gas-phase metallicity (at 4.6σ), and the observed far-ultraviolet absolute magnitude (at 3.4σ). Using previous observations of β1550obs at high redshift, we estimate the evolution of fesc, LyC with both redshift and galaxy magnitude. The LzLCS observations suggest that fainter and lower mass galaxies dominate the ionizing photon budget at higher redshift, possibly due to their rapidly evolving metal and dust content. Finally, we use our correlation between β1550obs and fesc, LyC × ξion to predict the ionizing emissivity of galaxies during the epoch of reionization. Our estimated emissivities match IGM observations, and suggest that star-forming galaxies emit sufficient LyC photons into the IGM to exceed recombinations near redshifts of 7–8.
|
|
| 14. |
|
|
| 15. |
- Finlator, Kristian, et al.
(författare)
-
The minimum halo mass for star formation at z=6-8
- 2017
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 464:2, s. 1633-1639
-
Tidskriftsartikel (refereegranskat)abstract
- Recent analysis of strongly lensed sources in the Hubble Frontier Fields indicates that the rest-frame UV luminosity function of galaxies at z=6-8 rises as a power law down to M-UV=-15, and possibly as faint as-12.5. We use predictions from a cosmological radiation hydrodynamic simulation to map these luminosities on to physical space, constraining the minimum dark matter halo mass and stellar mass that the Frontier Fields probe. While previously published theoretical studies have suggested or assumed that early star formation was suppressed in haloes less massive than 10(9)-10(11) M-circle dot, we find that recent observations demand vigorous star formation in haloes at least as massive as (3.1, 5.6, 10.5) x10(9) M-circle dot at z =(6, 7, 8). Likewise, we find that Frontier Fields observations probe down to stellar masses of (8.1, 18, 32) x10(6) M-circle dot: that is, they are observing the likely progenitors of analogues to Local Group dwarfs such as Pegasus and M32. Our simulations yield somewhat different constraints than two complementary models that have been invoked in similar analyses, emphasizing the need for further observational constraints on the galaxy-halo connection.
|
|
| 16. |
|
|
