Context. Planetary nebulae (PNe) are a brief but important phase of stellar evolution. The study Galactic PNe has historically been hampered by uncertain distances, the parallaxes PN central stars (CSPNe) measured Gaia improving situation. Aims. Gaia's Early Data Release 3 (EDR3) offers higher astrometric precision and greater completeness compared to previous releases. Taking advantage these i...

From a new mosaic image in the Hα line of the complete disc of the spiral galaxy M100, a catalogue is composed listing 1948 individual H ii regions. I give details of the data collection and reduction procedure, and of the production of the H ii region catalogue. For each H ii region, the catalogue gives its position relative to the centre of the galaxy, its deprojected distance to the centre, ...

Context. The majority of stars form in clusters. Therefore a comprehensive view of star formation requires understanding the initial conditions for cluster formation. Aims. The goal of our study is to shed light on the physical properties of infrared dark clouds (IRDCs) and the role they play in the formation of stellar clusters. This article, the first of a series dedicated to the study of IRD...

Context. α Centauri is our closest stellar neighbor, at a distance of only 1.3 pc, and its two main components have spectral types comparable to the Sun. This is therefore a favorable target for an imaging search for extrasolar planets. Moreover, indications exist that the gravitational mass of α Cen B is higher than its modeled mass, the difference being consistent with a substellar companion ...

The initial Phoenix Deep Survey (PDS) observations with the Australia Telescope Compact Array have been supplemented by additional 1.4GHz observations over the past few years. Here we present details of the construction of a new mosaic image covering an area of 4.56 square degrees, an investigation of the reliability of the source measurements, and the 1.4GHz source counts for the compiled radi...

An automated search for star clusters close to the Galactic plane (|b| < 5) was carried out on the Point Source Catalogue of the DENIS survey. 44% of the Galactic plane have been observed and calibrated. The method allowed to retrieve 22 known star clusters and to identify two new ones, not published yet although previously presented in the 2MASS web site as embedded clusters in HII regions. Ex...

We present BVRI photometry of 180 bright, southern nearby-star candidates. The stars were selected from the New Luyten Two-Tenths proper motion catalogue based on optical/infrared colours, constructed by combining Luytens’s mr estimates with nearinfrared photometry from the 2-Micron All Sky Survey. Photometric parallaxes derived from (V-KS), (V-I) and (I-J) colours, combined with the limited av...

We have constructed an analytical model to simulate the behavior of an adaptive optics system coupled with a sodium laser guide star. The code is applied to a 3.6-m and 8m class telescopes. The results are given in terms of Strehl ratio and full width at half maximum of the point spread function. Two atmospheric models are used, one representing good atmospheric conditions (20 per cent of the t...