The cosmic evolution of dust-corrected metallicity in the neutral gas

Interpreting abundances of Damped Ly-$\alpha$ Absorbers (DLAs) from absorption-line spectroscopy has typically been a challenge because of the presence of dust. Nevertheless, because DLAs trace distant gas-rich galaxies regardless of their luminosity, they provide an attractive way of measuring the evolution of the metallicity of the neutral gas with cosmic time. This has been done extensively so far, but typically not taking proper dust corrections into account. The aims of this paper are to: i) provide a simplified way of calculating dust corrections, based on a single observed [$X$/Fe], ii) assess the importance of dust corrections for DLA metallicities and their evolution, and iii) investigate the cosmic evolution of iron for a large DLA sample. We have derived dust corrections based on the observed [Zn/Fe], [Si/Fe], or [S/Fe], and confirmed their robustness. We present dust-corrected metallicities in a scale of [Fe/H]$_{\rm tot}$ for 236 DLAs over a broad range of $z$, and assess the extent of dust corrections for different metals at different metallicities. Dust corrections in DLAs are important even for Zn (typically of 0.1-0.2, and up to $0.5$~dex), which is often neglected. Finally, we study the evolution of the dust-corrected metallicity with $z$. The DLA metallicities decrease with redshift, by a factor of 50-100 from today to $\sim12.6$ billion years ago ($z=5$). When including dust corrections, the average DLA metallicities are 0.4--0.5~dex higher than without corrections. The upper envelope of the relation between metallicity and $z$ reaches solar metallicity at $z\lesssim0.5$, although some systems can have solar metallicity already out to $z\sim3$.Comment: Forthcoming in A&A. 16 pages, 5 figures, 3 table

Root Contrastiveness and V2: A Supra-Informational Status The Case of Two North-Eastern Italian Dialects

In the literature on Romance and Germanic V2, the fronted XP in the preverbal field is generally described as pragmatically salient, tacitly implying a crucial relationship between the V2 phenomenon and information structure. The degree to which discourse-pragmatics is pervasive in the V2 syntax is subject to cross-linguistic variation; nevertheless, the discussion of the phenomenon is often marginal in the literature. This paper sheds more light on the interaction between the V2 constraint and information structure by investigating two North-Eastern Italian dialects, Lamonat and Sovramontino, whose V2 constraint is solely linked to the unpackaging of discourse-pragmatic information. V2-motivated T-to-C movement ensures: (i) adjacency of the verb to the pragmatically salient element that, hence, receives discourse prominence; and (ii) the correct interpretation of contrastive elements, which are structurally realised in the preverbal field. The investigation of contrastive XPs suggests that contrastiveness should be regarded as an independent discourse-pragmatic status that supersedes topic and focus. In this respect, contrastiveness should not be considered a categorical notion, but a continuum in which the degree of contrastiveness is determined by the properties of the set containing the contrastive element

Metals and dust in the neutral ISM: the Galaxy, Magellanic Clouds, and damped Lyman-{\alpha} absorbers

Context. The presence of dust in the neutral interstellar medium (ISM) dramatically changes the metal abundances that we measure. Understanding the metal content in the neutral ISM, and a direct comparison between different environments, has been hampered to date because of the degeneracy to the observed ISM abundances caused by the effects of metallicity, the presence of dust, and nucleosynthesis. Aims. We study the metal and dust content in the neutral ISM consistently in different environments, and assess the universality of recently discovered sequences of relative abundances. We also intend to assess the validity of [Zn/Fe] as a tracer of dust in the ISM. This has recently been cast into doubt based on observations of stellar abundances, and needs to be addressed before we can safely use it to study the ISM. Methods. In this letter we present a simple comparison of relative abundances observed in the neutral ISM in the Galaxy, the Magellanic Clouds, and damped Lyman-{\alpha} Absorbers (DLAs). The main novelty in this comparison is the inclusion of the Magellanic Clouds. Results. The same sequences of relative abundances are valid for the Galaxy, Magellanic Clouds, and DLAs. These sequences are driven by the presence of dust in the ISM and seem 'universal'. Conclusions. The metal and dust properties in the neutral ISM appear to follow a similar behaviour in different environments. This suggests that a dominant fraction of the dust budget is built up from grain growth in the ISM depending of the physical conditions and regardless of the star formation history of the system. In addition, the DLA gas behaves like the neutral ISM, at least from a chemical point of view. Finally, despite the deviations in [Zn/Fe] observed in stellar abundances, [Zn/Fe] is a robust dust tracer in the ISM of different environments, from the Galaxy to DLAs.Comment: A&A Letter in press. 4 pages, 2 figure

On the (in)variance of the dust-to-metals ratio in galaxies

Recent works have demonstrated a surprisingly small variation of the dust-to-metals ratio in different environments and a correlation between dust extinction and the density of stars. Naively, one would interpret these findings as strong evidence of cosmic dust being produced mainly by stars. But other observational evidence suggest there is a significant variation of the dust-to-metals ratio with metallicity. As we demonstrate in this paper, a simple star-dust scenario is problematic also in the sense that it requires that destruction of dust in the interstellar medium (e.g., due to passage of supernova shocks) must be highly inefficient. We suggest a model where stellar dust production is indeed efficient, but where interstellar dust growth is equally important and acts as a replenishment mechanism which can counteract the effects of dust destruction. This model appears to resolve the seemingly contradictive observations, given that the ratio of the effective (stellar) dust and metal yields is not universal and thus may change from one environment to another, depending on metallicity.Comment: 10 pages, 4 figures. Accepted for publication in MNRA

Light Curves of Hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory

We investigate the light-curve properties of a sample of 26 spectroscopically confirmed hydrogen-poor superluminous supernovae (SLSNe-I) in the Palomar Transient Factory survey. These events are brighter than SNe Ib/c and SNe Ic-BL, on average, by about 4 and 2 mag, respectively. The peak absolute magnitudes of SLSNe-I in rest-frame g band span −22 ≾ M g ≾ −20 mag, and these peaks are not powered by radioactive ^(56)Ni, unless strong asymmetries are at play. The rise timescales are longer for SLSNe than for normal SNe Ib/c, by roughly 10 days, for events with similar decay times. Thus, SLSNe-I can be considered as a separate population based on photometric properties. After peak, SLSNe-I decay with a wide range of slopes, with no obvious gap between rapidly declining and slowly declining events. The latter events show more irregularities (bumps) in the light curves at all times. At late times, the SLSN-I light curves slow down and cluster around the ^(56)Co radioactive decay rate. Powering the late-time light curves with radioactive decay would require between 1 and 10 M⊙ of Ni masses. Alternatively, a simple magnetar model can reasonably fit the majority of SLSNe-I light curves, with four exceptions, and can mimic the radioactive decay of ^(56)Co, up to ~400 days from explosion. The resulting spin values do not correlate with the host-galaxy metallicities. Finally, the analysis of our sample cannot strengthen the case for using SLSNe-I for cosmology

Mem?ria do trabalho, cultura e territ?rio quilombola

O presente artigo trata da pesquisa realizada com a Comunidade Quilombola situada no Distrito de S?o Paulo das Tunas, munic?pio de Giru?/RS. Conhecida como ?casas dos Morenos?,e reconhecida como Comunidade Quilombola Corr?a desde junho de 2010, quando foi registrada e certificada como tal pela Funda??o Cultural Palmares.A gera??o atual reside no Quilombo e tem como meio de subsist?ncia os produtos provenientes da propriedade rural e fundamentalmente a aposentadoria. O Quilombo Corr?a ? uma comunidade rural e est? situada na regi?o onde predominam moradores descendentes dos imigrantes de origem alem? e polonesa, a proposta ? compreender seus processos hist?ricos de forma??o e a constitui??o de estilos particulares de vida nesse contexto, assim como, costumes e identidades culturais s?o interseccionados com a sociedade envolvente. Interessa, portanto, tratar como os quilombolas, sujeitos etnicamente diferenciados nessa contextura, constroem sua identidade e seu cotidiano no local observando suas estrat?gias de sobreviv?ncia cultural. Assim, a pesquisa procurou descrever os ritmos e afazeres do cotidiano da fam?lia Corr?a, procurando recriar pela escrita as tramas narradas pela mem?ria do grupo

Dust-depletion sequences in damped Lyman-α absorbers II. The composition of cosmic dust, from low-metallicity systems to the Galaxy

Metals in the interstellar medium (ISM) of essentially all types of galaxies are observed to be depleted compared to the expected values. The depletion is most likely due to dust condensation in, for example, cold molecular clouds and various circumstellar and interstellar environments. The relative observed metal abundances should thereby reflect the composition of the ISM dust components. We aim at identifying the most dominant dust species or types, including silicate and iron oxide grains present in the ISM, using recent observations of dust depletion of galaxies at various evolutionary stages. We use the observed elemental abundances in dust of several metals (O, S, Si, Mg, and Fe) in different environments, considering systems with different metallicities and dust content, namely damped Lyman-α absorbers (DLAs) towards quasars and the Galaxy. We derive a possible dust composition by computationally finding the statistically expected elemental abundances in dust assuming a set of key dust species with the iron content as a free parameter. Carbonaceous dust is not considered in the present study. Metallic iron (likely in the form of inclusions in silicate grains) and iron oxides are important components of the mass composition of carbon-free dust. The latter make up a significant mass fraction (~1∕4 in some cases) of the oxygen-bearing dust and there are good reasons to believe that metallic iron constitutes a similar mass fraction of dust. Wüstite (FeO) could be a simple explanation for the depletion of iron and oxygen because it is easily formed. There appears to be no silicate species clearly dominating the silicate mass, but rather a mix of iron-poor as well as iron-rich olivine and pyroxene. To what extent sulphur depletion is due to sulfides remains unclear. In general, there seems to be little evolution of the dust composition (not considering carbonaceous dust) from low-metallicity systems to the Galaxy

436 - Amendements aux articles 65, 87 et 88 du règlement intérieur du Conseil Interaméricain de l’Agriculture et ratification des amendements aux articles 73, 96 et 97 du Règlement Intérieur du Comité Exécutif

(WD-320) Ratification of the Amendments to the rules of procedure of the Executive Committee and the IAB