By compiling abundances from red and blue supergiants (SGs) within the Local Universe, I present the Mass-Metallicity relation (MZR) using stellar tracers, demonstrating the excellent internal consistency. Comparing this result with nebular tracers, those empirically calibrated to direct-method studies provide the most consistent results.

Red Supergiant Stars (RSGs) are important probes of stellar and chemical evolution in star-forming environments. They represent the brightest near-IR stellar components of external galaxies and probe the most recent stellar population to provide robust, independent abundance estimates. The Local Group dwarf irregular galaxy, NGC6822, is a reasonably isolated galaxy with an interesting structure and turbulent history. Using RSGs as chemical abundance probes, we estimate metallicities in the central region of NGC6822, finding a suggestion of a metallicity gradient (in broad agreement with nebular tracers), however, this requires further study for confirmation. With intermediate resolution Multi-object spectroscopy (from e.g. KMOS, EMIR, MOSFIRE) combined with state-of-the-art stellar model atmospheres, we demonstrate how RSGs can be used to estimate stellar abundances in external galaxies. In this context, we compare stellar and nebular abundance tracers in NGC 6822 and by combining stellar and nebular tracers we estimate an abundance gradient of −0.18 ± 0.05 dex/kpc.

We carried out a pivot experiment to select distant luminous late-type stars on the basis on their 2MASS and GLIMPSE photometry. Low-resolution infrared spectra enabled us to measure the equivalent widths (EWs) of their CO band-heads at 2.293 μm, and to confirm an extraordinarily high detection rate of red supergiants (RSGs), i.e. 61% (Messineo et al. (2016)).

In this study, we examine the effect of surface density of disks on chemical evolution of galaxies. We find that, higher surface brightness galaxies on average possess higher gas-phase metallicity compared to lower surface brightness galaxies with the same stellar and gas mass. The surface brightness effect is more significant for low-mass galaxies. Using an analytical model of chemical evolution involving gas outflow and accretion, we find that the surface brightness dependence can be attributed to the strength of inflowing pristine gas. Galaxies with lower surface brightness experience stronger inflow than galaxies with a higher surface brightness of a similar mass.

We conducted infrared spectroscopic observations of bright stars in the direction of the molecular clouds W33 and GMC G23.3 − 0.3. We compared stellar spectro-photometric distances with parallactic distances to these regions, and we were able to assess the association of the detected massive stars with these molecular complexes. The spatial and temporal distributions of the detected stars enabled us to locate sources of ionizing radiation and to gather precise information on the star formation history of these clouds. The studied clouds present different distributions of massive stars.

A few core collapse supernovae progenitors have been found to be yellow or blue supergiants. Weshall discuss possible scenarios involving single and close binary evolution allowing to explain this kind of corecollapse supernova progenitors. According to stellar models for both single and close binaries, blue supergiants, at theend of their nuclear lifetimes and thus progenitors of core collapse supernovae, present very different characteristicsfor what concerns their surface compositions, rotational surface velocities and pulsational properties with respect toblue supergiants in their core helium burning phase. We discuss how the small observed scatter of the flux-weightedgravity-luminosity (FWGL) relation of blue supergiants constrains the evolution of massive stars after the Main-Sequence phase and the nature of the progenitors of supernovae in the mass range between 12 and 40 solarmasses. The present day observed surface abundances of blue supergiants, of their pulsational properties, as well asthe small scatter of the FWGL relation provide strong constraints on both internal mixing and mass loss in massivestars and therefore on the end point of their evolution.

Different from previous triennial reports, this report covers the activities of IAU Commission 36 ‘Theory of Stellar Atmospheres’ over the past six years†, and will be the last report from the ‘old’ Commission 36. After the General Assembly in Honolulu (August 2015), a new Commission ‘Stellar and Planetary Atmospheres’ (C.G5, under Division G, ‘Stars and Stellar Physics’) has come into life, and will continue our work devoted to the outer envelopes of stars, as well as extend it to the atmospheres of planets (see Sect. 4).

High-redshift quasars are unique probes of the evolution of supermassive black holes and the intergalactic medium at the end of the epoch of reionization. We present the optical spectra of eight new z ~ 6 quasars selected from the Panoramic Survey Telescope & Rapid Response System 1 (Pan-STARRS1). Details of the selection strategy can be found in Bañados et al. (2014). With this work we increase the number of known quasars at z < 5.7 by more than 10%. The quasars discovered here span a large range of luminosities (19.6 ≤ zP1 ≤ 21.2) and are remarkably heterogeneous in their spectral features: half of them show bright emission lines whereas the other half show weak or no Lyα emission line. We find a larger fraction of weak–line emission quasars than in lower redshift studies, although still based on low number statistics, this may imply that the quasar population could be more diverse than previously thought.

The business meeting of IAU Commission 36 took place during the GA in Beijing on August 27th, and its major topic was the re-structuring of the IAU Divisions and consequences for our Commission. The meeting was conducted by the new president, Joachim Puls, since the past president (still in charge during the GA), Martin Asplund, could not participate.

We have re-appraised the temperatures of Red Supergiants (RSGs) in the Magellanic Clouds, by studying their spectral energy distributions (SEDs) from 400–2500 nm using VLT+XSHOOTER, in conjunction with MARCS model atmospheres. We determine temperatures using 3 methods: from model fits to the TiO bands in the optical; from model fits to the SED using the line-free continuum in the near-infrared; and from the integrated fluxes. We find that the temperatures from the TiO fits are systematically lower that those from the other methods by several hundred Kelvin. The TiO fits also dramatically over-predict the flux in the near-IR, and imply extinctions which are anomalously low compared to neighbouring stars. In contrast, the SED temperatures provide good fits to the fluxes at all wavelengths other than the TiO bands, are in agreement with the temperatures from the flux integration method, and imply extinctions consistent with nearby stars. We consider a number of ways to reconcile this discrepancy, concluding that 3-D effects are responsible, and that RSG temperatures are much warmer than previously thought.

The chemical abundances of galaxies provide key constraints to models of their formation and evolution. Unfortunately, the standard method of determining abundances, from the strong emission lines of Hii-regions, is well-known to be subject to large systematic errors, particularly at high metallicities. To address this problem we are currently working on a project to measure a galaxy’s chemical abundances from spectral analysis of individual RSGs. By focussing on a spectral window in the J-band which contains few molecular lines, we are able to derive accurate chemical abundances from relatively low resolution data. In fact, we show that this technique can operate at distances of 3–4 Mpc using the VLT, and a factor of 10 further if we target massive RSG-dominated star clusters. Furthermore, in the ELT-era, we show that we can perform abundance analysis on individual stars out to 70 Mpc, and redshifts of 0.1 for star clusters.

Red supergiants with their enormous brightness at J-band are ideal probes of cosmic chemical composition. It is therefore crucial to have realistic models of radiative transfer in their atmospheres, which will permit determination of abundances accurate to 0.15 dex, the precision attainable with future telescope facilities in galaxies as distant as tens of Mpc. Here, we study the effects of non-local thermodynamic equilibrium (NLTE) on the formation of iron, titanium, and silicon lines, which dominate J-band spectra of red supergiants. It is shown that the NLTE radiative transfer models enable accurate derivation of metallicity and effective temperature in the J-band. We also discuss consequences for RSG spectrum synthesis in different spectral windows, including the heavily TiO-blanketed optical region, and atmospheric structure. We then touch upon challenges of NLTE integration with new generation of 3D hydrodynamical RSG models and present the first calculations of NLTE spectra with the mean 3D model of Betelgeuse.

We present a precise and accurate measurement of the distance to the Large Magellanic Cloud based on late-type eclipsing-binary systems. Our results provide curently the most accurate zero point for the extragalactic distance scale.

Division IX provides a forum for astronomers engaged in the planning, development, construction, and calibration of optical and infrared telescopes and instrumentation, as well as observational procedures including data processing. A few years ago, discussions were started about changes in the structure of Division IX, with the aim of bringing it more in line with today's world of large coordinated projects and multi-national observatories. The course of this process, and further steps to be taken in the period from 2009 to 2012, were at the focus of the deliberations at the business meeting of Division IX at the IAU General Assembly in Rio de Janeiro.

We have chosen the name of GYES, one of the mythological giants with one hundred arms,offspring of Gaia and Uranus, for our instrument study of a multifibre spectrograph forthe prime focus of the Canada-France-Hawaii Telescope. Such an instrument could provide anexcellent ground-based complement for the Gaia mission and a northern complement to theHERMES project on the AAT. The CFHT is well known for providing a stable prime focusenvironment, with a large field of view, which has hosted several imaging instruments, buthas never hosted a multifibre spectrograph. Building upon the experience gained at GÉPIwith FLAMES-Giraffe and X-Shooter, we are investigating the feasibility of a highmultiplex spectrograph (about 500 fibres) over a field of view one degree in diameter. Weare investigating an instrument with resolution in the range 15 000 to 30 000, whichshould provide accurate chemical abundances for stars down to 16th magnitude and radialvelocities, accurate to 1 km s-1 for fainter stars. The study is led byGÉPI-Observatoire de Paris with a contribution from Oxford for the study of thepositioner. The financing for the study comes from INSU CSAA and Observatoire de Paris.The conceptual study will be delivered to CFHT for review by October 1st 2010.

Division IX provides a forum for astronomers engaged in the innovation, development and calibration of optical instrumentation and observational procedures including data processing.

We describe the implementation and accuracy of slitless radial velocity measurements of extragalactic PNs with Subaru and the FOCAS spectrograph. As a first application of the method, we have extended a previous study of PNs in NGC 4697 to larger angular distances from its center, failing again to find evidence of dark matter in this elliptical galaxy.

This document introduces the reports by the Commissions and Working Groups of Division IX.

The next generation of ground-based telescopes will give access to resolved stellar populations in previously unexplored environments. To highlight the potential for stellar spectroscopy using an extremely large telescope (ELT), we present data from an ongoing project with the Very Large Telescope (VLT) to calibrate a novel method of distance determination. An ELT would extend the reach of this method and would allow quantitative studies of individual stars well beyond the Local Group, sampling a wide range of galaxy morphologies and metallicities.