On the variation in stellar alpha-enhancements of star-forming galaxies in the EAGLE simulation

The ratio of $\alpha$-elements to iron in galaxies holds valuable information about the star-formation history since their enrichment occurs on different timescales. The fossil record of stars in galaxies has mostly been excavated for passive galaxies, since the light of star-forming galaxies is dominated by young stars which have much weaker atmospheric absorption features. Here we use the cosmological EAGLE simulation to investigate the origin of variations in $\alpha$-enhancement among star-forming galaxies at $z=0$. The definition of $\alpha$-enhancement in a composite stellar population is ambiguous. We elucidate two definitions - termed 'mean' and 'galactic' $\alpha$-enhancement - in more detail. While a star-forming galaxy has a high 'mean' $\alpha$-enhancement when its stars formed rapidly, a galaxy with a large 'galactic' $\alpha$-enhancement generally had a delayed star formation history. We find that absorption-line strengths of Mg and Fe correlate with variations in $\alpha$-enhancement. These correlations are strongest for the 'galactic' $\alpha$-enhancement. However, we show that these are mostly caused by other effects which are cross-correlated with $\alpha$-enhancement, such as variations in the light-weighted age. This severely complicates the retrieval of $\alpha$-enhancements in star-forming galaxies. The ambiguity is not severe for passive galaxies and we confirm that spectral variations in these galaxies are caused by measurable variations in $\alpha$-enhancements. We suggest that this more complex coupling between $\alpha$-enhancement and star formation histories can guide the interpretation of new observations of star-forming galaxies.Comment: 16 pages, 12 figures, 4 tables. Submitted to MNRAS. Comments/hints for missing citations are very welcome

The atomic-to-molecular hydrogen transition in the TNG50 simulation:Using realistic UV fields to create spatially resolved H i maps

Cold gas in galaxies provides a crucial test to evaluate the realism of cosmological hydrodynamical simulations. To extract the atomic and molecular hydrogen properties of the simulated galaxy population, post-processing methods taking the local UV field into account are required. We improve upon previous studies by calculating realistic UV fields with the dust radiative transfer code SKIRT to model the atomic-to-molecular transition in TNG50, the highest-resolution run of the IllustrisTNG suite. Comparing integrated quantities such as the H i mass function, we study to what detail the UV field needs to be modelled in order to calculate realistic cold gas properties. We then evaluate new, spatially resolved comparisons for cold gas in galaxies by exploring synthetic maps of atomic hydrogen at redshift zero and compare them to 21-cm observations of local galaxies from the WHISP survey. In terms of non-parametric morphologies, we find that TNG50 H i maps are less concentrated than their WHISP counterparts (median ΔC ≈ 0.3), due in part to central H i deficits related to the ejective character of supermassive black hole feedback in TNG. In terms of the H i column density distribution function, we find discrepancies between WHISP and IllustrisTNG that depend on the total H i abundance in these data sets as well as the post-processing method. To fully exploit the synergy between cosmological simulations and upcoming deep H i/H2 data, we advocate the use of accurate methods to estimate the UV radiation field and to generate mock maps.</p

Orthodox Religious Organizations in the Context of Transformation of State-Confessional Relations (1985-1997): Problems And Features (the Case of the Dagestan Republic)

The increased importance of the religious factor, which influences various aspects of social life, has made it relevant for current academic research. The interrelation of this factor with the political history of Russia makes it one of the most complex and priority areas in the confessional policy of the State, and provokes the rethinking of Russia’s policy in the national regions. The issues related to the relationship between official authorities and Orthodox organizations in polyconfessional regions with a predominance of Muslim populations, particularly in Dagestan are of particular interest for us. The absence of historical interpretations on the history of Orthodox organizations in the transitional and post-Soviet periods makes the stated subject topical for identifying and introducing into scientific circulation a specific material that regional studies can provide. Proceeding from the above, in the proposed paper for the first time in regional historiography we’ve made an attempt to consider the transformation processes in the socio-political situation in the country during the transitional and first decade of the post-Soviet period (1985-1997) and their influence on the development of the Orthodox religion, Christian believers and clergy in Dagestan. We’ve made conclusion about the latent process of religious orthodox revival in the republic against the background of the general spiritual crisis in the country during the transitional period of history, conditioned by the continuing policy of “state atheism”. Atheistic worldview of governing bodies often influenced the process of building relationships with religious organizations and was characterized as “ambiguous”. Religious renaissance in the first half of the 1990s in Dagestan had its own local features, due to the deterioration of the socio-political background of the republic and was accompanied by factors that adversely affect the position of Orthodoxy here. Authots’ contribution: O.B. Khalidova is responsible for the idea, literature review, data interpretation, paper compilation and edition; G.F. Gebekov has carried out the analysis and intepretation of sociological poll data

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS)

Ultra-hot Jupiters offer interesting prospects for expanding our theories on dynamical evolution and the properties of extremely irradiated atmospheres. In this context, we present the analysis of new optical spectroscopy for the transiting ultra-hot Jupiter WASP-121b. We first refine the orbital properties of WASP-121b, which is on a nearly polar (obliquity ψ North=88.1±0.25° or ψ South=91.11±0.20°) orbit, and exclude a high differential rotation for its fast-rotating (P<1.13 days), highly inclined (i*North?=8.1+3.0°−2.6° or i*South=171.9+2.5°−3.4) star. We then present a new method that exploits the reloaded Rossiter-McLaughlin technique to separate the contribution of the planetary atmosphere and of the spectrum of the stellar surface along the transit chord. Its application to HARPS transit spectroscopy of WASP-121b reveals the absorption signature from metals, likely atomic iron, in the planet atmospheric limb. The width of the signal (14.3±1.2 km s⁻¹) can be explained by the rotation of the tidally locked planet. Its blueshift (-5.2±0.5 km s⁻¹)could trace strong winds from the dayside to the nightside, or the anisotropic expansion of the planetary thermosphere

Alkaline Signatures of an Active Exomoon

Stars and planetary system

Sodium and Potassium Signatures of Volcanic Satellites Orbiting Close-in Gas Giant Exoplanets

International audienceExtrasolar satellites are generally too small to be detected by nominal searches. By analogy to the most active body in the solar system, Io, we describe how sodium (Na I) and potassium (K I) gas could be a signature of the geological activity venting from an otherwise hidden exo-Io. Analyzing ∼a dozen close-in gas giants hosting robust alkaline detections, we show that an Io-sized satellite can be stable against orbital decay below a planetary tidal 10 p 11. This tidal energy is also focused into the satellite driving an ∼10 5±2 higher mass-loss rate than Io's supply to Jupiter's Na exosphere based on simple atmospheric loss estimates. The remarkable consequence is that several exo-Io column densities are, on average, more than sufficient to provide the ∼10 10±1 Na cm −2 required by the equivalent width of exoplanet transmission spectra. Furthermore, the benchmark observations of both Jupiter's extended (∼1000 R J) Na exosphere and Jupiter's atmosphere in transmission spectroscopy yield similar Na column densities that are purely exogenic in nature. As a proof of concept, we fit the "high-altitude" Na at WASP-49b with an ionization-limited cloud similar to the observed Na profile about Io. Moving forward, we strongly encourage time-dependent ingress and egress monitoring along with spectroscopic searches for other volcanic volatiles

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS): IV. A spectral inventory of atoms and molecules in the high-resolution transmission spectrum of WASP-121 b

status: publishe