We present results from an ongoing programme to study the dust and ionized gas in E/S0 galaxies with dust lanes. Our data, together with results from previous studies of E/S0 galaxies, are used to demonstrate the close relationship between these two components. This relationship is discussed in light of our current understanding of the nature and origin of the interstellar medium (ISM), and in particular in the context of the interplay between the different multi‐temperature components. We show that focusing on dust obscured regions as tracers of the ISM, and on their properties, serves as independent evidence for the external origin of the dust and ionized gas.

We present our H α observations of 11 isolated southern galaxies: SDIG, PGC 51659, E 222-010, E 272-025, E 137-018, IC 4662, Sag DIG, IC 5052, IC 5152, UGCA 438, and E 149-003, with distances from 1 to 7 Mpc. We have determined the total H α fluxes from these galaxies. The star formation rates in these galaxies range from 10 −1 (IC 4662) to 10 −4 M ⊙ yr −1 (SDIG) and the gas depletion time at the observed star formation rates lies within the range from 1/6 to 24 Hubble times H −1 0 .

In the framework of an ongoing project aimed at searching for and studying eXtremely Metal-Poor (XMP) very gas-rich blue dwarfs in nearby voids, we conducted spectroscopy with the 11-m Southern African Large Telescope (SALT) of 26 candidates, preselected in the first paper of this series (PEPK19). For 23 of them, we detected Oxygen lines, allowing us to estimate the gas O/H ratio. For ten of them, the oxygen abundance is found to be very low, in the range of 12+log(O/H)=6.95-7.30 dex. Of those, four void dwarfs have 12+log(O/H) < 7.19, or Z < Z /30. For the majority of observed galaxies, the faint line [Oiii]λ4363Å used to estimate O/H with the direct T e method appeared either too noisy or was not detected. We therefore use the semiempirical method of Izotov & Thuan (2007) for these spectra, or, when applicable, the new 'Strong line' method of Izotov et al. (2019b). We present and discuss the results for all void dwarfs observed in this work. We also compare their O/H values with O/H values of ∼140 void galaxies available from our recent papers. We address the properties of the newly found unusual void XMP dwarfs and compare them with those for ten known prototype void XMP objects. The latter small group is outstanding based on their very small mass fraction of stars (only 0.01-0.02 of the baryonic mass), the blue colours of stars in the outer body (indicating a non-cosmological age for the main star-forming episode), and the low gas metallicity (several times lower than expected for their luminosity).

Eleven periodic variable stars were observed photometrically through two to four filters from the set UBVR C I C . Phase-folded data for each star cover full cycles of variation. Spectral energy distributions, based on absolute photometry extracted from the literature, are used to inform models of the stars. The stars include four eclipsing systems with hot subdwarfs of spectral type O or B (sdO/B). Periods are in the range 1.8–2.2 hr. Four reflection-effect binaries, with amplitudes as large as 0.5 mag in the R C filter were observed; periods range from 1.6 to 2.4 hr. In two of these latter systems, the primary stars are also sdB stars, while two have white-dwarf components. In all eight of these binaries the companion stars are probably M dwarfs. The remaining three stars are pulsators: one large-amplitude δ Scuti star previously misclassified as an eclipsing system; one field SX Phe star near the Galactic plane; and one multiperiodic high-luminosity star of unknown type. The amplitude is usually a strong function of the wavelength in pulsating stars, but this is not the case for the high-luminosity variable. One possible explanation is that the luminous star has a pulsating companion. The SX Phe and high-luminosity star are both heavily reddened (A V > 5 mag).

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One of the important sources for independent determination of stellar masses is eclipsing binaries with components on the main sequence, and with observable spectral lines of both components. The parameters of such stars are used to construct the mass–luminosity relation for stars of high and intermediate masses. Among them, the type of long-period eclipsing binaries stands out, the parameters of which are currently not fully determined, which is associated with the difficulties caused by the need for long-term observations. In this article, we will review the currently available observational data for such objects and discuss the prospects for their use to determine stellar masses.

Abstract.We discuss the opportunities to use the future ELTs to study in detail the properties and the evolution peculiarities of individual massive stars with a metal content typical of galaxies in the Universe during the first 0.5-1Gyr, corresponding to the earliest known newly formed galaxies at redshifts of z = 6 − 10. This is possible in principle due to the existence in the local Universe of starbursting galaxies with metallicities of ∼1/30 Z . The nearest such galaxies are DDO 68 at ∼6.5 Mpc with 12+log(O/H) = 7.21 and I Zw 18 at 15 Mpc with 12+log(O/H) = 7.17. For the youngest star clusters (with ages of T < 4-5Myr) in these most metal-poor galaxies, stars with masses up to 40-60 M should be present on both the Main Sequence and the later evolution stages, including the WR stage. They are expected to have apparent magnitudes as bright as V = 21 m for DDO 68 and V = 23 m for I Zw 18. Good S/Nratio spectroscopy with telescopes like OWL or JWST, allowing near-milli-arcsecond angular resolution, will provide unique information to check the most up-to-date models of massive star evolution in the very low metallicity regime, and thus, establish a firm basis to model the effects of star formation in 'primordial' galaxies, at the epoch of galaxy formation. Such observations will also provide an independent channel to probe the primordial Helium abundance.

We have completed our observational programme to search for wide binary systems&#xD; with non-coeval components in the southern sky and report our results here.&#xD; The final set of four systems was spectroscopically investigated in this paper. No binary systems&#xD; with components of different ages were found among them. Taking into account our previous studies,&#xD; we estimate the fraction of such binaries (i.e., binaries formed, presumably, by capture)&#xD; not higher than 0.06 per cent.&#xD; The study will be continued on the northern sky.