We present a 4.7σ detection of the [OIII] 88 μm line in a gravitationally-lensed Lyman break galaxy, RXC J2248-ID3, using the Atacama Large Millimeter/submillimeter Array (ALMA). We did not detect [CII] 158 μm and rest-frame 90 μm dust continuum emission, suggesting that the bulk of the interstellar medium (ISM) is ionized. Our two-component SED model combining the previous Hubble Space Telescope (HST) data and new photometry obtained from Very Large Telescope (VLT), Spitzer and ALMA suggests the presence of young (∼2 Myr) and mature (∼600 Myr) stellar components with the metallicity of Z = 0.2Z⊙. Our findings are in contrast with previous results claiming a very young, metal-poor stellar component.

Dust attenuation shapes the spectral energy distributions of galaxies and any modelling and fitting procedure of their spectral energy distributions must account for this process. We present results of two recent works dedicated at measuring the dust attenuation curves in star forming galaxies at redshift from 0.5 to 3, by fitting continuum (photometric) and line (spectroscopic) measurements simultaneously with CIGALE using variable attenuation laws based on flexible recipes. Both studies conclude to a large variety of effective attenuation laws with an attenuation law flattening when the obscuration increases. An extra attenuation is found for nebular lines. The comparison with radiative transfer models implies a flattening of the attenuation law up to near infrared wavelengths, which is well reproduced with a power-laws recipe inspired by the Charlot and Fall recipe. Here we propose a global modification of the Calzetti attenuation law to better reproduce the results of radiative transfer models.

Heiiλ1640 emission in the absence of other metal lines is the most sought-after emission line to detect and characterize metal free stellar populations. However, even recent stellar population models with sophisticated treatment of stellar evolution also lack sufficient He+ ionising photons to reproduce observed He 0.1em ii fluxes. We use VLT/MUSE GTO observations to compile a catalogue of 15 z ∼ 2–4 He ii λ1640 emitters from ∼10–30 hour pointings. We show that both He ii λ1640 detections and non-detections occupy similar distribution in UV absolute magnitudes. Rest-UV emission line analysis of our sample shows that the emission lines of our He ii λ1640 emitters are driven by star-formation in solar to moderately sub-solar (∼1/20th) metallicity conditions. However, we find that even after considering effects from binary stars, we are unable to reproduce the He ii λ1640 equivalent widths. Alternative mechanisms are necessary to compensate for the missing He+ ionising photons.

We used the spectroscopic and astrometric data provided from the GALactic Archaeology with HERMES (GALAH) Data Release (DR2) and Gaia DR2, respectively, for a large sample of stars to investigate the behaviour of the [ $\alpha$ /Fe] abundances via two procedures, that is, kinematically and spectroscopically. With the kinematical procedure, we investigated the distribution of the [ $\alpha$ /Fe] abundances into the high-/low-probability thin disc, and high-/low-probability thick-disc populations in terms of total space velocity, [Fe/H] abundance, and age. The high-probability thin-disc stars dominate in all sub-intervals of [ $\alpha$ /Fe], including the rich ones: [ $\alpha$ /Fe] $\,>\,0.3$ dex, where the high-probability thick-disc stars are expected to dominate. This result can be explained by the limiting apparent magnitude of the GALAH DR2 ( $V \lt 14$ mag) and intermediate galactic latitude of the star sample. Stars in the four populations share equivalent [ $\alpha$ /Fe] and [Fe/H] abundances, total space velocities, and ages. Hence, none of these parameters can be used alone for separation of a sample of stars into different populations. High-probability thin-disc stars with abundance $-1.3 \lt {\rm[Fe/H]}\leq -0.5$ dex and age $9 \lt \tau\leq13$ Gyr are assumed to have different birth places relative to the metal-rich and younger ones. With the spectroscopic procedure, we separated the sample stars into $\alpha$ -rich and $\alpha$ -poor categories by means of their ages as well as their [ $\alpha$ /Fe] and [Fe/H] abundances. Stars older than 8 Gyr are richer in [ $\alpha$ /Fe] than the younger ones. We could estimate the abundance [ $\alpha$ /Fe] = 0.14 dex as the boundary separating the $\alpha$ -rich and $\alpha$ -poor sub-samples in the [ $\alpha$ /Fe] $\,\times\,$ [Fe/H] plane.