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Only 5% of what makes up the Universe is well understood, and it consists of baryonic matter and radiation. Dark matter and energy correspond to the remaining 95% of the Universe, and their origin and evolution have not yet been satisfactorily explained. Dark matter, supposedly present in the galaxies' halo region, appears to be the mechanism that causes the unusual behavior of the stars' tangential velocity, which is higher than that predicted by the interaction with visible matter. With the solutions of the equations of motion for spacetime generated by a spinning cosmic string with an internal structure in Brans-Dicke gravitation, the present work aimed to evaluate whether this type of string can play the role currently defined as that of dark matter, which is to originate the typical rotational curves of galaxies, responsible for maintaining the tangential velocities of the stars that form these galaxies, whose behavior cannot be justified solely by the observed baryonic matter. For this, the model was used to obtain the velocities of the stars of 4 Sc-type galaxies, to be compared with their respective experimentally observed values., Comment: 11 pages, 2 figures, text in Portuguese, work presented at the 23a. Mostra de Ensino, Pesquisa e Extens\~ao, IFRS, C\^ampus Porto Alegre, 2023

Electric failures are a problem for customers and grid operators. Identifying causes and localizing the source of failures in the grid is critical. Here, we focus on a specific power grid in the Arctic region of North Norway. First, we collect data pertaining to the grid topology, the topography of the area, the historical meteorological data, and the historical energy consumption/production data. Then, we exploit statistical and machine-learning techniques to predict the occurrence of failures. We interpret the variables that mostly explain the classification results to be the main driving factors of power interruption. We are able to predict 57% (F1-score 0.53) of all failures reported over a period of 1 year with a weighted support-vector machine model. Wind speed and local industry activity are found to be the main controlling parameters where the location of exposed power lines is a likely trigger. In summary, we discuss causing factors for failures in the power grid and enable the distribution system operators to implement strategies to prevent and mitigate incoming failures., Comment: 25 pages, 8 Figures. A full-length article that is under review in the Applied Energy Journal

We measure the evolution of the rest-frame UV luminosity function (LF) and the stellar mass function (SMF) of Lyman-alpha (Lya) emitters (LAEs) from z~2 to z~6 by exploring ~4000 LAEs from the SC4K sample. We find a correlation between Lya luminosity (LLya) and rest-frame UV (M_UV), with best-fit M_UV=-1.6+-0.2 log10(LLya/erg/s)+47+-12 and a shallower relation between LLya and stellar mass (Mstar), with best-fit log10( Mstar/Msun)=0.9+-0.1 log10(LLya/erg/s)-28+-4.0. An increasing LLya cut predominantly lowers the number density of faint M_UV and low Mstar LAEs. We estimate a proxy for the full UV LFs and SMFs of LAEs with simple assumptions of the faint end slope. For the UV LF, we find a brightening of the characteristic UV luminosity (M_UV*) with increasing redshift and a decrease of the characteristic number density (Phi*). For the SMF, we measure a characteristic stellar mass (Mstar*/Msun) increase with increasing redshift, and a Phi* decline. However, if we apply a uniform luminosity cut of log10 (LLya/erg/s) >= 43.0, we find much milder to no evolution in the UV and SMF of LAEs. The UV luminosity density (rho_UV) of the full sample of LAEs shows moderate evolution and the stellar mass density (rho_M) decreases, with both being always lower than the total rho_UV and rho_M of more typical galaxies but slowly approaching them with increasing redshift. Overall, our results indicate that both rho_UV and rho_M of LAEs slowly approach the measurements of continuum-selected galaxies at z>6, which suggests a key role of LAEs in the epoch of reionisation., Comment: Accepted for publication in MNRAS. 20 pages, 13 figures, 4 tables

We present the first results from the X-SHOOTER Lyman-$\alpha$ survey at $z=2$ (XLS-$z2$). XLS-$z2$ is a deep spectroscopic survey of 35 Lyman-$\alpha$ emitters (LAEs) utilising $\approx90$ hours of exposure time with VLT/X-SHOOTER and covers rest-frame Ly$\alpha$ to H$\alpha$ emission with R$\approx4000$. We present the sample selection, the observations and the data reduction. Systemic redshifts are measured from rest-frame optical lines for 33/35 sources. In the stacked spectrum, our LAEs are characterised by an interstellar medium with little dust, a low metallicity and a high ionisation state. The ionising sources are young hot stars that power strong emission-lines in the optical and high ionisation lines in the UV. The LAEs exhibit clumpy UV morphologies and have outflowing kinematics with blue-shifted SiII absorption, a broad [OIII] component and a red-skewed Ly$\alpha$ line. Typically 30 % of the Ly$\alpha$ photons escape, of which one quarter on the blue side of the systemic velocity. A fraction of Ly$\alpha$ photons escapes directly at the systemic suggesting clear channels enabling a $\approx10$ % escape of ionising photons, consistent with an inference based on MgII. A combination of a low effective HI column density, a low dust content and young star-burst determine whether a star forming galaxy is observed as a LAE. The first is possibly related to outflows and/or a fortunate viewing angle, while we find that the latter two in LAEs are typical for their stellar mass of 10$^9$ M$_{\odot}$., Comment: Main text 26 pages. Accepted for publication in MNRAS

Since the inception of the atomic force microscope AFM, dynamic methods have been very fruitful by establishing methods to quantify dissipative and conservative forces in the nanoscale and by providing a means to apply gentle forces to the samples with high resolution. Here we review developments that cover over a decade of our work on energy dissipation, phase contrast and the extraction of relevant material properties from observables. We describe the attempts to recover material properties via one dimensional amplitude and phase curves from force models and explore the evolution of these methods in terms of force reconstruction, fits of experimental measurements, and the more recent advances in multifrequency AFM.

We explore deep rest-frame UV to FIR data in the COSMOS field to measure the individual spectral energy distributions (SED) of the ~4000 SC4K (Sobral et al. 2018) Lyman-alpha (Lya) emitters (LAEs) at z~2-6. We find typical stellar masses of 10$^{9.3\pm0.6}$ M$_{\odot}$ and star formation rates (SFR) of SFR$_{SED}=4.4^{+10.5}_{-2.4}$ M$_{\odot}$/yr and SFR$_{Lya}=5.9^{+6.3}_{-2.6}$ M$_{\odot}$/yr, combined with very blue UV slopes of beta=-2.1$^{+0.5}_{-0.4}$, but with significant variations within the population. M$_{UV}$ and beta are correlated in a similar way to UV-selected sources, but LAEs are consistently bluer. This suggests that LAEs are the youngest and/or most dust-poor subset of the UV-selected population. We also study the Lya rest-frame equivalent width (EW$_0$) and find 45 "extreme" LAEs with EW$_0>240$ A (3 $\sigma$), implying a low number density of $(7\pm1)\times10^{-7}$ Mpc$^{-3}$. Overall, we measure little to no evolution of the Lya EW$_0$ and scale length parameter ($w_0$) which are consistently high (EW$_0=140^{+280}_{-70}$ A, $w_0=129^{+11}_{-11}$ A) from z~6 to z~2 and below. However, $w_0$ is anti-correlated with M$_{UV}$ and stellar mass. Our results imply that sources selected as LAEs have a high Lya escape fraction (f$_{esc, Lya}$) irrespective of cosmic time, but f$_{esc, Lya}$ is still higher for UV-fainter and lower mass LAEs. The least massive LAEs ($<10^{9.5}$ M$_{\odot}$) are typically located above the star formation "Main Sequence" (MS), but the offset from the MS decreases towards z~6 and towards $10^{10}$ M$_{\odot}$. Our results imply a lack of evolution in the properties of LAEs across time and reveals the increasing overlap in properties of LAEs and UV-continuum selected galaxies as typical star-forming galaxies at high redshift effectively become LAEs., Comment: Accepted for publication in MNRAS. 23 pages, 11 figures, 3 tables + appendices. The full SC4K catalogue of LAEs with PSF photometry, stellar masses, SFRs and other properties for individual LAEs, is available at https://goo.gl/q9yfKo

Despite recent progress in understanding Lyman-alpha (Lya) emitters (LAEs), relatively little is known regarding their typical black hole activity across cosmic time. Here, we study the X-ray and radio properties of ~4000 LAEs at 2.23) and find an average luminosity of 10^{44.31+-0.01} erg/s and an average black hole accretion rate (BHAR) of 0.72+-0.01 Msun/yr, consistent with moderate to high accreting AGN. We detect 120 sources in deep radio data (radio AGN fraction of 3.2%+-0.3%). The global AGN fraction (8.6%+-0.4%) rises with Lya luminosity and declines with increasing redshift. For X-ray detected LAEs, Lya luminosities correlate with the BHARs, suggesting that Lya luminosity becomes an accretion rate indicator. Most LAEs (93.1+-0.6%) at 2

The observed properties of the Lyman-$\alpha$ (Ly$\alpha$) emission line are a powerful probe of neutral gas in and around galaxies. We present spatially resolved Ly$\alpha$ spectroscopy with VLT/MUSE targeting VR7, a UV-luminous galaxy at $z=6.532$ with moderate Ly$\alpha$ equivalent width (EW$_0\approx38$ {\AA}). These data are combined with deep resolved [CII]$_{\rm 158 \mu m}$ spectroscopy obtained with ALMA and UV imaging from {\it HST} and we also detect UV continuum with MUSE. Ly$\alpha$ emission is clearly detected with S/N $\approx40$ and FWHM of 374 km s$^{-1}$. Ly$\alpha$ and [CII] are similarly extended beyond the UV, with effective radius r$_{\rm eff} = 2.1\pm0.2$ kpc for a single exponential model or r$_{\rm eff, Ly\alpha, halo} = 3.45^{+1.08}_{-0.87}$ kpc when measured jointly with the UV continuum. The Ly$\alpha$ profile is broader and redshifted with respect to the [CII] line (by 213 km s$^{-1}$), but there are spatial variations that are qualitatively similar in both lines and coincide with resolved UV components. This suggests that the emission originates from two components with plausibly different HI column densities. We place VR7 in the context of other galaxies at similar and lower redshift. The Ly$\alpha$ halo scale length is similar at different redshifts and velocity shifts with respect to the systemic are typically smaller. Overall, we find little indications of a more neutral vicinity at higher redshift. This means that the local ($\sim 10$ kpc) neutral gas conditions that determine the observed Ly$\alpha$ properties in VR7 resemble the conditions in post-re-ionisation galaxies., Comment: 13 pages, 10 figures. Accepted for publication in MNRAS