Aims. We determine the metallicities of globular clusters (GCs) in the WLM and IKN dwarf galaxies, using VLT/UVES and Keck/ESI spectroscopy. These measurements are combined with literature data for ...field stars to constrain GC formation scenarios. For the WLM GC, we also measure detailed abundance ratios for a number of light, α, Fe-peak, and n-capture elements, which are compared with literature data for the Fornax dSph and the Milky Way. Methods. The abundances are derived by computing synthetic integrated-light model spectra and adjusting the input composition until the best fits to the observed spectra are obtained. Results. We find low metallicities of Fe/H = −2.0 and −2.1 for the WLM GC and the GC IKN-5, respectively. We estimate that 17%–31% of the stars with Fe/H ≤ −2 in WLM belong to the GC, and IKN-5 may even contain a similar number of metal-poor stars as the whole of the IKN dwarf itself. While these fractions are much higher than in the Milky Way halo, we have previously found a similarly high ratio of metal-poor GCs to field stars in the Fornax dSph. The overall abundance patterns in the WLM GC are similar to those observed for GCs in the Fornax dSph: the Ca/Fe and Ti/Fe ratios are super-Solar at about +0.3 dex, while Mg/Fe is less elevated than Ca/Fe and Ti/Fe. The Na/Fe ratio is similar to the averaged Na/Fe ratios in Milky Way GCs, but higher (by ~2σ) than those of Milky Way halo stars. Iron-peak (Mn, Sc, Cr) and heavy elements (Ba, Y, La) generally follow the trends seen in the Milky Way halo. Conclusions. The GCs in the WLM and IKN dwarf galaxies resemble those in the Fornax dSph by being significantly more metal-poor than a typical halo GC in the Milky Way and other large galaxies. They are also substantially more metal-poor than the bulk of the field stars in their parent galaxies. It appears that only a small fraction of the Milky Way GC system could have been accreted from galaxies similar to these dwarfs. The relatively high Na abundance in the WLM GC suggests that the Na/O anti-correlation is present in this cluster, while the high ratios of metal-poor GCs to field stars in the dwarfs are in tension with GC formation scenarios that require GCs to have lost a very large fraction of their initial mass.
ABSTRACT The presence of star-to-star light-element abundance variations (also known as multiple populations, MPs) appears to be ubiquitous within old and massive clusters in the Milky Way and all ...studied nearby galaxies. Most previous studies have focused on resolved images or spectroscopy of individual stars, although there has been significant effort in the past few years to look for multiple population signatures in integrated light spectroscopy. If proven feasible, integrated light studies offer a potential way to vastly open parameter space, as clusters out to 10s of Mpc can be studied. We use the Na D lines in the integrated spectra of two clusters with similar ages (2–3 Gyr) but very different masses: NGC 1978 (∼3 × 105 M⊙) in the Large Magellanic Cloud and G114 (1.7 × 107 M⊙) in NGC 1316. For NGC 1978, our findings agree with resolved studies of individual stars that did not find evidence for Na spreads. However, for G114, we find clear evidence for the presence of multiple populations. The fact that the same anomalous abundance patterns are found in both the intermediate age and ancient globular clusters lends further support to the notion that young massive clusters are effectively the same as the ancient globular clusters, only separated in age.
Strategies for biomarker discovery increasingly focus on biofluid protein and peptide expression patterns. Post-translational modifications contribute significantly to the pattern complexity and ...thereby increase the likelihood of obtaining specific biomarkers for diagnostics and disease monitoring. Glycosylation is a common post-translational modification that plays a role e.g. in cell adhesion and in cell-cell and receptor-ligand interactions. Abnormal protein glycosylation has important disease associations, and the glycoproteome is therefore a target for biomarker discovery. Here we present a simple and highly selective strategy for purification of sialic acid-containing glycopeptides (the sialiome) from complex peptide mixtures. The approach utilizes a high and selective affinity of sialic acids for titanium dioxide under specific buffer conditions. In combination with mass spectrometry we used this strategy to characterize the human plasma and saliva sialiomes where 192 and 97 glycosylation sites, respectively, were identified. Furthermore we illustrate the potential of this method in biomarker discovery.
We recently found the globular cluster (GC) EXT8 in M 31 to have an extremely low metallicity of Fe/H = −2.91 ± 0.04 using high-resolution spectroscopy. Here we present a colour–magnitude diagram ...(CMD) for EXT8, obtained with the Wide Field Camera 3 on board the
Hubble
Space Telescope. Compared with the CMDs of metal-poor Galactic GCs, we find that the upper red giant branch (RGB) of EXT8 is ∼0.03 mag bluer in
M
F
606
W
−
M
F
814
W
and slightly steeper, as expected from the low spectroscopic metallicity. The observed colour spread on the upper RGB is consistent with being caused entirely by the measurement uncertainties, and we place an upper limit of
σ
F
606
W
−
F
814
W
≈ 0.015 mag on any intrinsic colour spread. The corresponding metallicity spread can be up to
σ
Fe/H
∼ 0.2 dex or > 0.7 dex, depending on the isochrone library adopted. The horizontal branch is located mostly on the blue side of the instability strip and has a tail extending to at least
M
F
606
W
= +3, as in the Galactic GC M 15. We identify two candidate RR Lyrae variables and several ultraviolet-luminous post-horizontal-branch and/or post-asymptotic-giant-branch star candidates, including one very bright (
M
F
300
X
≈ −3.2) source near the centre of EXT8. The surface brightness of EXT8 out to a radius of 25″ is well fitted by a Wilson-type profile with an ellipticity of
ϵ
= 0.20, a semi-major axis core radius of 0.″25, and a central surface brightness of
μ
F
606
W
, 0
= 15.2 mag arcsec
−2
, with no evidence of extra-tidal structure. Overall, EXT8 has properties consistent with it being a ‘normal’, but very metal-poor, GC, and its combination of relatively high mass and very low metallicity thus remains challenging to explain in the context of GC formation theories operating within the hierarchical galaxy assembly paradigm.
Injury to the glomerular podocyte is a key mechanism in human glomerular disease and podocyte repair is an important therapeutic target. In Fabry disease, podocyte injury is caused by the ...intracellular accumulation of globotriaosylceramide. This study identifies in the human podocyte three endocytic receptors, mannose 6-phosphate/insulin-like growth II receptor, megalin, and sortilin and demonstrates their drug delivery capabilities for enzyme replacement therapy. Sortilin, a novel α-galactosidase A binding protein, reveals a predominant intracellular expression but also surface expression in the podocyte. The present study provides the rationale for the renal effect of treatment with α-galactosidase A and identifies potential pathways for future non-carbohydrate based drug delivery to the kidney podocyte and other potential affected organs.
We present new deep imaging of the central regions of the remote globular cluster NGC 2419, obtained with the F343N and F336W filters of the Wide Field Camera 3 on board the Hubble Space Telescope. ...The new data are combined with archival imaging to constrain nitrogen and helium abundance variations within the cluster. We find a clearly bimodal distribution of the nitrogen-sensitive F336W–F343N colours of red giants, from which we estimate that about 55% of the giants belong to a population with about normal (field-like) nitrogen abundances (P1), while the remaining 45% belong to a nitrogen-rich population (P2). On average, the P2 stars are more He-rich than the P1 stars, with an estimated mean difference of ΔY ≃ 0.05, but the P2 stars exhibit a significant spread in He content and some may reach ΔY ≃ 0.13. A smaller He spread may also be present for the P1 stars. Additionally, stars with spectroscopically determined low Mg abundances (Mg/Fe < 0) are generally associated with P2. We find the P2 stars to be slightly more centrally concentrated in NGC 2419 with a projected half-number radius of about 10% less than for the P1 stars, but the difference is not highly significant (p ≃ 0.05). Using published radial velocities, we find evidence of rotation for the P1 stars, whereas the results are inconclusive for the P2 stars, which are consistent with no rotation as well as the same average rotation found for the P1 stars. Because of the long relaxation time scale of NGC 2419, the radial trends and kinematic properties of the populations are expected to be relatively unaffected by dynamical evolution. Hence, they provide constraints on formation scenarios for multiple populations, which must account not only for the presence of He spreads within sub-populations identified via CNO variations, but also for the relatively modest differences in the spatial distributions and kinematics of the populations.
ABSTRACT
Recent work has shown that the properties of multiple populations (MPs) within massive stellar clusters (i.e. in the extent of their abundance variations as well as the fraction of stars ...that show the anomalous chemistry) depend on the mass as well as the age of the host cluster. Such correlations are largely unexpected in current models for the formation of MPs and hence provide essential insight into their origin. Here, we extend our previous study into the presence or absence of MPs using integrated light spectroscopy of the ∼600 Myr, massive (∼107–108 M⊙) clusters, W3 and W30, in the galactic merger remnant, NGC 7252. Due to the extreme mass of both clusters, the expectation is that they should host rather extreme abundance spreads, manifested through high mean Na/Fe abundances. However, we do not find evidence for a strong Na/Fe enhancement, with the observations being consistent with the solar value. This suggests that age is playing a key role, or alternatively that MPs only manifest below a certain stellar mass, as the integrated light at all ages above ∼100 Myr is dominated by stars near or above the main-sequence turn-off.
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