703 research outputs found
Disappearing galaxies: the orientation dependence of JWST-bright, HST-dark, star-forming galaxy selection
Galaxies that are invisible in deep optical-NIR imaging but detected at
longer wavelengths have been the focus of several recent observational studies,
with speculation that they could constitute a substantial missing population
and even dominate the cosmic star formation rate density at . The
depths now achievable with JWST at the longest wavelengths probed by HST,
coupled with the transformative resolution at longer wavelengths, are already
enabling detailed, spatially-resolved characterisation of sources that were
invisible to HST, often known as `HST-dark' galaxies. However, until now, there
has been little theoretical work to compare against. We present the first
simulation-based study of this population, using highly-resolved galaxies from
the Feedback in Realistic Environments (FIRE) project, with multi-wavelength
images along several lines of sight forward-modelled using radiative transfer.
We naturally recover a population of modelled sources that meet commonly-used
selection criteria ( and
). These simulated HST-dark galaxies lie at high
redshifts (), have high levels of dust attenuation (), and
display compact recent star formation
(). Orientation is very
important: for all but one of the 17 simulated galaxy snapshots with HST-dark
sightlines, there exist other sightlines that do not meet the criteria. This
result has important implications for comparisons between observations and
models that do not resolve the detailed star-dust geometry, such as
semi-analytic models or coarsely-resolved hydrodynamical simulations.
Critically, we demonstrate that HST-dark sources are not an unexpected or
exotic population, but a subset of high-redshift, highly-dust-attenuated
sources viewed along certain lines of sight.Comment: 12 pages, 8 figures. Accepted for publication in Ap
Dense nanostructured zirconia compacts obtained by colloidal filtration of binary mixtures
As starting materials two commercial nanosized zirconias doped with 3 mol% of Y 2O 3 were used: a powder of about 100 nm (TZ3YE, Tosoh, Japan) and a colloidal suspension of about 15 nm (Mel Chemicals, UK). Colloidal stability in water was studied for both zirconias in terms of zeta potential as a function of deflocculant concentration and pH. Concentrated suspensions were prepared by dispersing the powder in the colloidal suspension to solids loadings ranging from 5 to 30 vol.% using a sonication probe to achieve dispersion. The rheological behavior was optimized in terms of solids content, deflocculant content and sonication time. Optimized suspensions with up to 25 vol.% solids showed a nearly Newtonian behavior and extremely low viscosities and maintain stable for long times (days) which is an important drawback of conventional nanoparticle suspensions. Samples obtained by slip casting in plaster moulds were used for dynamic sintering studies and dense, nanostructured specimens were obtained at temperatures of 1300-1400°C.This work has been supported by Spanish Ministry of Science and Innovation (Projects MAT2009-14144-C03-02 and MAT2009-14369-C02-01). R. Moreno thanks to Universidad Politecnica de Valencia for the concession of a grant in the frame of its Programme of Support to R + D (PAID-02-11, R-1752).Benavente Martínez, R.; Salvador Moya, MD.; Alcázar, M.; Moreno, R. (2012). Dense nanostructured zirconia compacts obtained by colloidal filtration of binary mixtures. Ceramics International. 38(3):2111-2117. https://doi.org/10.1016/j.ceramint.2011.10.051S2111211738
The potential role of the adipokine HMGB1 in obesity and insulin resistance. Novel effects on adipose tissue biology
Discovery of the adipose tissue as a major source of signaling molecules almost three decades ago set a novel physiological paradigm that paved the way for the identification of metabolic organs as endocrine organs. Adipocytes, the main adipose tissue cell type, do not only represent the principal site of energy storage in form of triglycerides, but also produce a variety of molecules for short and long distance intercellular communication, named adipokines, which coordinate systemic responses. Although the best known adipokines identified and characterized hitherto are leptin and adiponectin, novel adipokines are continuously being described, what have significantly helped to elucidate the role of adipocyte biology in obesity and associated comorbidities. One of these novel adipokines is high-mobility group box 1 (HMGB1), a ubiquitous nuclear protein that has been recently reported to be dysregulated in obese dysfunctional adipocytes. Although the classical function of HMGB1 is related to inflammation and immunity, acting as an alarmin, novel advances evidence an active implication of HMGB1 in tissue remodeling and fibrosis. This review summarizes the current evidence on the mechanisms controlling HMGB1 release, as well as its role as a regulator of adipocyte function and extracellular matrix remodeling, with special emphasis on the potential of this novel adipokine as a target in the obesity treatment
Beware the recent past: a bias in spectral energy distribution modelling due to bursty star formation
We investigate how the recovery of galaxy star formation rates (SFRs) using
energy-balance spectral energy distribution (SED) fitting codes depends on
their recent star formation histories (SFHs). We use the Magphys and Prospector
codes to fit 6,706 synthetic spectral energy distributions (SEDs) of simulated
massive galaxies at from the Feedback in Realistic Environments
(FIRE) project. We identify a previously unknown systematic error in the
Magphys results due to bursty star formation: the SFR estimates of individual
galaxies can differ from the true values by as much as 1 dex, at large
statistical significance (), depending on the details of their recent
SFH. The SFRs inferred using Prospector do not exhibit this trend, likely
because unlike Magphys, Prospector uses non-parametric SFHs. We urge caution
when using Magphys, or other codes assuming parametric SFHs, to study galaxies
where the average SFR may have changed significantly over the last 100
Myr, such as those which have recently quenched their star formation or those
experiencing an ongoing burst. This concern is especially relevant, for
example, when fitting JWST observations of very high-redshift galaxies.Comment: 5 pages, 3 figures, submitted to MNRAS Letter
Beware the recent past: a bias in spectral energy distribution modelling due to bursty star formation
© 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/We investigate how the recovery of galaxy star formation rates (SFRs) using energy-balance spectral energy distribution (SED) fitting codes depends on their recent star formation histories (SFHs). We use the Magphys and Prospector codes to fit 6,706 synthetic spectral energy distributions of simulated massive galaxies at ), depending on the details of their recent SFH. SFRs inferred using Prospector with non-parametric SFHs do not exhibit this trend. We show that using parametric SFHs (pSFHs) causes SFR uncertainties to be underestimated by a factor of up to . Although this undoubtedly contributes to the significance of the systematic, it cannot explain the largest biases in the SFRs of the starbursting galaxies, which could be caused by details of the stochastic prior sampling or the burst implementation in the Magphys libraries. We advise against using pSFHs and urge careful consideration of starbursts when SED modelling galaxies where the SFR may have changed significantly over the last ~100 Myr, such as recently quenched galaxies, or those experiencing a burst. This concern is especially relevant, e.g. when fitting JWST observations of very high-redshift galaxies.Peer reviewe
Inositol Pyrophosphate-Controlled Kinetochore Architecture and Mitotic Entry in S. pombe
Inositol pyrophosphates (IPPs) comprise a specific class of signaling molecules that regulate central biological processes in eukaryotes. The conserved Vip1/PPIP5K family controls intracellular IP8 levels, the highest phosphorylated form of IPPs present in yeasts, as it has both inositol kinase and pyrophosphatase activities. Previous studies have shown that the fission yeast S. pombe Vip1/PPIP5K family member Asp1 impacts chromosome transmission fidelity via the modulation of spindle function. We now demonstrate that an IP8 analogue is targeted by endogenous Asp1 and that cellular IP8 is subject to cell cycle control. Mitotic entry requires Asp1 kinase function and IP8 levels are increased at the G2/M transition. In addition, the kinetochore, the conductor of chromosome segregation that is assembled on chromosomes is modulated by IP8. Members of the yeast CCAN kinetochore-subcomplex such as Mal2/CENP-O localize to the kinetochore depending on the intracellular IP8-level: higher than wild-type IP8 levels reduce Mal2 kinetochore targeting, while a reduction in IP8 has the opposite effect. As our perturbations of the inositol polyphosphate and IPP pathways demonstrate that kinetochore architecture depends solely on IP8 and not on other IPPs, we conclude that chromosome transmission fidelity is controlled by IP8 via an interplay between entry into mitosis, kinetochore architecture, and spindle dynamics.Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)Medical Research Council (MRC)Peer Reviewe
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