204 research outputs found
Recalibrating the cosmic star formation history
The calibrations linking observed luminosities to the star formation rate
depend on the assumed stellar population synthesis model, initial mass
function, star formation and metal enrichment history, and whether reprocessing
by dust and gas is included. Consequently the shape and normalisation of the
inferred cosmic star formation history is sensitive to these assumptions. Using
v2.2.1 of the Binary Population and Spectral Synthesis (\bpass) model we
determine a new set of calibration coefficients for the ultraviolet,
thermal-infrared, and, hydrogen recombination lines. These ultraviolet and
thermal infrared coefficients are 0.15-0.2 dex higher than those widely
utilised in the literature while the H coefficient is dex
larger. These differences arise in part due to the inclusion binary evolution
pathways but predominantly reflect an extension in the IMF to 300
and a change in the choice of reference metallicity. We use these new
coefficients to recalibrate the cosmic star formation history, and find
improved agreement between the integrated cosmic star formation history and the
in-situ measured stellar mass density as a function of redshift. However, these
coefficients produce new tension between star formation rate densities inferred
from the ultraviolet and thermal-infrared and those from H.Comment: 7 pages, 8 figures, accepted for publication in MNRA
Eggshell pigment composition covaries with phylogeny but not with life history or with nesting ecology traits of British passerines
No single hypothesis is likely to explain the diversity in eggshell coloration and patterning across birds, suggesting that eggshell appearance is most likely to have evolved to fulfill many nonexclusive functions. By controlling for nonindependent phylogenetic associations between related species, we describe this diversity using museum eggshells of 71 British breeding passerine species to examine how eggshell pigment composition and concentrations vary with phylogeny and with life-history and nesting ecology traits. Across species, concentrations of biliverdin and protoporphyrin, the two main pigments found in eggshells, were strongly and positively correlated, and both pigments strongly covaried with phylogenetic relatedness. Controlling for phylogeny, cavity-nesting species laid eggs with lower protoporphyrin concentrations in the shell, while higher biliverdin concentrations were associated with thicker eggshells for species of all nest types. Overall, these relationships between eggshell pigment concentrations and the biology of passerines are similar to those previously found in nonpasserine eggs, and imply that phylogenetic dependence must be considered across the class in further explanations of the functional significance of avian eggshell coloration
Dynamics of former ice lobes of the southernmost Patagonian Ice Sheet based on a glacial landsystems approach
PMN J1632-0033: A new gravitationally lensed quasar
We report the discovery of a gravitationally lensed quasar resulting from our
survey for lenses in the southern sky. Radio images of PMN J1632-0033 with the
VLA and ATCA exhibit two compact, flat-spectrum components with separation
1.47" and flux density ratio 13.2. Images with the HST reveal the optical
counterparts to the radio components and also the lens galaxy. An optical
spectrum of the bright component, obtained with the first Magellan telescope,
reveals quasar emission lines at redshift 3.42. Deeper radio images with MERLIN
and the VLBA reveal a faint third radio component located near the center of
the lens galaxy, which is either a third image of the background quasar or
faint emission from the lens galaxy.Comment: 21 pp., including 4 figures; thoroughly revised in light of new
MERLIN/HST data; accepted for publication in A
The Quintuple Quasar: Radio and Optical Observations
We present results from high-resolution radio and optical observations of PMN
J0134-0931, a gravitational lens with a unique radio morphology and an
extremely red optical counterpart. Our data support the theory of Keeton & Winn
(2003): five of the six observed radio components are multiple images of a
single quasar, produced by a pair of lens galaxies. Multi-frequency VLBA maps
show that the sixth and faintest component has a different radio spectrum than
the others, confirming that it represents a second component of the background
source rather than a sixth image. The lens models predict that there should be
additional faint images of this second source component, and we find evidence
for one of the predicted images. The previously-observed large angular sizes of
two of the five bright components are not intrinsic (which would have excluded
the possibility that they are lensed images), but are instead due to scatter
broadening. Both the extended radio emission observed at low frequencies, and
the intrinsic image shapes observed at high frequencies, can be explained by
the lens models. The pair of lens galaxies is marginally detected in HST
images. The differential extinction of the quasar images suggests that the
extreme red color of the quasar is at least partly due to dust in the lens
galaxies.Comment: ApJ, in press. 22 pp, 10 fig
Late-Onset Erythropoietic Porphyria Caused by a Chromosome 18q Deletion in Erythroid Cells
The erythropoietic porphyrias, erythropoietic protoporphyria and congenital erythropoietic porphyria, result from germline mutations in the ferrochelatase gene and uroporphyrinogen III synthase gene, respectively. Both conditions normally present in childhood but rare cases with onset past the age of 40 y have been reported. Here we show that late-onset erythropoietic protoporphyria can be caused by deletion of the ferrochelatase gene in hematopoietic cells with clonal expansion as part of the myelodysplastic process. This is the first direct demonstration of porphyria produced by an acquired molecular defect restricted to one tissue. Some other cases of late-onset erythropoietic porphyria may be explained by a similar mechanism
Impacts of colonial waterbirds on vegetation and potential restoration of island habitats
Colonial waterbirds have impacted forested island ecosystems throughout their breeding range, changing vegetation, and soil characteristics and bird communities. Our objectives were to (1) determine effects of three levels of colonial waterbird exclusion on overall vegetation diversity and growth, and survival of a candidate restoration species (black elderberry; Sambucus nigra canadensis); (2) investigate effects of different planting techniques on survival and growth of black elderberry; and (3) determine effects of waterbird colonization on soil chemistry. In 2012, we investigated effects of three levels of waterbird exclusion (none control plots [CON]; partial, which excluded waterbirds larger than gulls [PEX]; and full which excluded all waterbirds [FEX]) on bird use, existing vegetation growth and diversity, and survival of planted black elderberry on three islands in Door County, WI, Lake Michigan. In 2013, we evaluated survival of black elderberry established with four planting treatments within three waterbird exclusion treatments on two islands in 2013.We also compared soil chemistry characteristics between islands with and without nesting waterbirds for 2 years. Overall plant growth was greater in exclosures, but elderberry survival was similar among treatments. Soil replacement and weed suppression planting treatments did not affect survival, but generally increased overall elderberry biomass. Soil from nesting islands was more acidic and had greater nutrient concentrations than reference islands. Exclusion or removal of colonial nesting waterbirds from islands may improve overall vegetation growth, but successful restoration of woody vegetation may require significant soil manipulation and planting
iMaNGA: mock MaNGA galaxies based on IllustrisTNG and MaStar SSPs. -- III. Stellar metallicity drivers in MaNGA and TNG50
The iMaNGA project uses a forward-modelling approach to compare the
predictions of cosmological simulations with observations from SDSS-IV/MaNGA.
We investigate the dependency of age and metallicity radial gradients on galaxy
morphology, stellar mass, stellar surface mass density (), and
environment. The key of our analysis is that observational biases affecting the
interpretation of MaNGA data are emulated in the theoretical iMaNGA sample. The
simulations reproduce the observed global stellar population scaling relations
with positive correlations between galaxy mass and age/metallicity quite well
and also produce younger stellar populations in late-type in agreement with
observations. We do find interesting discrepancies, though, that can inform the
physics and further development of the simulations. Ages of spiral galaxies and
low-mass ellipticals are overestimated by about 2-4 Gyr. Radial metallicity
gradients are steeper in iMaNGA than in MaNGA, a discrepancy most prominent in
spiral and lenticular galaxies. Also, the observed steepening of metallicity
gradients with increasing galaxy mass is not well matched by the simulations.
We find that the theoretical radial profiles of surface mass density
are steeper than in observations except for the most massive galaxies. In both
MaNGA and iMaNGA [Z/H] correlates with , however, the simulations
systematically predict lower [Z/H] by almost a factor of 2 at any .
Most interestingly, for galaxies with stellar mass
the MaNGA data reveal a positive correlation between galaxy radius and [Z/H] at
fixed , which is not recovered in iMaNGA. Finally, the dependence on
environmental density is negligible in both the theoretical iMaNGA and the
observed MaNGA data
Psoriatic nail dystrophy is associated with erosive disease in the distal interphalangeal joints in psoriatic arthritis:a retrospective cohort study
Objective. To assess whether the association between psoriatic nail dystrophy and radiographic damage in the hands of patients with psoriatic arthritis (PsA) is specific to the distal interphalangeal (DIP) joints. Methods. A convenience sample of patients was collated from the Bath longitudinal PsA cohort. All patients had PsA according to the ClASsification for Psoriatic ARthritis criteria (CASPAR) criteria, scored radiographs of their hands, and documented nail scores as measured by the Psoriatic Nail Severity Score. Chi-square tests were performed to examine for association between features of nail dystrophy and radiographic damage in the DIP joints, and proximal interphalangeal or metacarpophalangeal (non-DIP) joints of the corresponding digits. Results. There were 134 patients included, with a median age of 53 years (interquartile range; IQR 44-61) and disease duration of 7 years (IQR 3-17). The presence of any form of psoriatic nail dystrophy was associated with erosion at the DIP joints of the corresponding digit (OR 1.9, 95% CI 1.23-2.83; p < 0.004) and this association was primarily driven by the presence of nail onycholysis (OR 1.72; 95% CI 1.12-2.62; p = 0.02). Nail subungual hyperkeratosis was more strongly associated with joint space narrowing, erosions, and osteoproliferation at the corresponding DIP joint compared to non-DIP joints (p < 0.001). Nail pitting was not associated with erosions or osteoproliferation. Conclusion. The presence of psoriatic nail dystrophy, particularly onycholysis, is associated with erosive disease at the DIP joints. Subungual hyperkeratosis is more strongly associated with erosive damage at the DIP than non-DIP joints. These findings support the anatomical and pathological link between nail and DIP joint disease.</p
ALMACAL. XI. Over-densities as signposts to proto-clusters? A cautionary tale
It may be unsurprising that the most common approach to finding
proto-clusters is to search for over-densities of galaxies. Upgrades to
submillimetre (submm) interferometers and the advent of the James Webb Space
Telescope will soon offer the opportunity to find more distant candidate
proto-clusters in deep sky surveys without any spectroscopic confirmation. In
this letter, we report the serendipitous discovery of an extremely dense region
centred on the blazar, J0217-0820, at z=0.6 in the ALMACAL sky survey. Its
density is eight times higher than that predicted by blind submm surveys. Among
the seven submm-bright galaxies, three are as bright as conventional
single-dish submm galaxies, with S_870um > 3mJy. The over-density is thus
comparable to the densest known and confirmed proto-cluster cores. However,
their spectra betray a wide range of redshifts. We investigate the likelihood
of line-of-sight projection effects using light cones from cosmological
simulations, finding that the deeper we search, the higher the chance that we
will suffer from such projection effects. The extreme over-density around
J0217-0820 demonstrates the strong cosmic variance we may encounter in the deep
submm surveys. Thus, we should also question the fidelity of galaxy
proto-cluster candidates selected via over-densities of galaxies, where the
negative K correction eases the detection of dusty galaxies along an
extraordinarily extended line of sight.Comment: 7 pages, 5 figures, update with the accepted versio
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