A good fraction of the Commission 55 (C55) Organizing Committee met in Beijing in August at the XXVIII IAU General Assembly, where C55 organized Special Session 14 (SpS14) entitled “Communicating Astronomy with the Public for Scientists.” During our C55 business meeting, and again during an impromptu gathering a few days later, we discussed changes in the IAU's organizational and programmatic structure and how these changes might affect C55. This report summarizes key points and offers some ideas about what we're calling “C55 v2.0.” For background and reference, see the C55 website at http://www.communicatingastronomy.org.

Is it physically feasible to perform the chromospheric diagnosis using spatial maps of scattering polarization at the solar disk center? To investigate it we synthesized polarization maps (in 8542 Å) resulting from MHD solar models and NLTE radiative transfer calculations that consider Hanle effect and vertical macroscopic motions. After explaining the physical context of forward scattering and presenting our results, we arrive at the definition of Hanle polarity inversion lines. We show how such features can give support for a clearer chromospheric diagnosis in which the magnetic and dynamic effects in the scattering polarization could be disentangled.

We investigate the origin of stellar metallicity gradients in massive galaxies at large radii (r > 2 Reff) using ten cosmological zoom simulations of halos with 6 × 1012M⊙ < Mhalo < 2 × 1013M⊙. The simulations follow metal cooling and enrichment from SNII, SNIa and AGB winds. We explore the differential impact of an empirical model for galactic winds that reproduces the evolution of the mass-metallicity relation. At larger radii, the galaxies become more dominated by stars accreted from satellite galaxies in major and minor mergers. In the wind model, fewer stars are accreted, but they are significantly more metal poor resulting in steep global metallicity (〈 ▽ Zstars 〉= -0.35 dex/dex) gradients in agreement with observations. Metallicity gradients of models without winds are inconsistent with observations. For the wind model, stellar accretion is steepening existing in-situ metallicity gradients by about 0.2 dex by the present day and is required to match observed gradients. Metallicity gradients are significantly steeper for systems, which have accreted stars in minor mergers. In contrast, galaxies with major mergers have relatively flat gradients, confirming previous results. We highlight the importance of stellar accretion for stellar population properties of massive galaxies at large radii, which provide important constraints for formation models.

Evolutionary scenarios suggest that several mechanisms (from inner secular evolution to accretion/merging) may transform galaxy members, driving groups from an active star forming phase to a more passive, typical of dense environments. We are investigating this transition in a nearby group sample, designed to cover a wide range of properties (see also Marino et al. (2010), Bettoni et al. (2011) and Marino et al. (2012)). We study two groups, USGC U268 and USGC U376 located in different regions of the Leo cloud, through a photometric and kinematic characterization of their member galaxies. We revisit the group membership, using results from recent red-shift surveys, and we investigate their substructures. U268, composed of 10 catalogued members and 11 new added members, has a small fraction (~24%) of early-type galaxies (ETGs). U376 has 16 plus 8 new added members, with ~38% of ETGs. We find the significant substructuring in both groups suggesting that they are likely accreting galaxies. U268 is located in a more loose environment than U376. For each member galaxy, broad band integrated and surface photometry have been obtained in far-UV (FUV) and near-UV (NUV) with GALEX, and in u, g, r, i, z (SDSS) bands. Hα imaging and 2D high resolution kinematical data have been obtained using PUMA Scanning Fabry-Perot interferometer at the 2.12 m telescope in San Pedro Mártir (Baja California, México). We improved the galaxy classification and we detected morphological and kinematical distortions that may be connected to either on-going and/or past interaction/accretion events or environmental induced secular evolution. U268 appears more active than U376, with a large fraction of galaxies showing interaction signatures (60% vs. 13%). The presence of bars among late-type galaxies is ~10% in U268 and 29% in U376. The cumulative distribution of (FUV - NUV) colors of galaxies in U268 is significantly different (bluer) than that of U376's galaxies. Most (80%) of the early-type members in U376 inhabits the red sequence, a large fraction of galaxies, of different morphological types, are located in the green valley, while the blue sequence is under-populated with respect to U268.

For 40 years, the sizes and shapes of many dozens of asteroids have been determined from observations of asteroidal occultations, and over a thousand high-precision positions of the asteroids relative to stars have been measured. Some of the first evidence for satellites of asteroids was obtained from the early efforts; now, the orbits and sizes of some satellites discovered by other means have been refined from occultation observations. Also, several close binary stars have been discovered, and the angular diameters of some stars have been measured from analysis of these observations. The International Occultation Timing Association (IOTA) coordinates this activity worldwide, from predicting and publicizing the events, to accurately timing the occultations from as many stations as possible, and publishing and archiving the observations.

The weak lensing effect generates spin-2 distortions, referred to as shear, on the observable shape of distant galaxies, induced by intervening gravitational tidal fields. Traditionally, the spin-2 distortion in the light distribution of distant galaxies is measured in terms of a galaxy ellipticity. This is a very good unbiased estimator of the shear field in the limit that a galaxy is measured at infinite signal-to-noise. However, the ellipticity is always defined as a ratio between two quantities (for example, between the polarisation and measurement of the galaxy size, or between the semi-major and semi-minor axis of the galaxy) and therefore requires some non-linear combination of the image pixels. This means, in any realistic case, this would lead to biases in the measurement of the shear (and hence in the cosmological parameters) whenever noise is present in the image. This type of bias can be understood from the particular shape of the 2D probability distribution of the ellipticity of an object measured from data. Moreover this probability distribution can be used to explore strategies for calibration of noise biases in present and future weak lensing surveys (e.g. KiDS, DES, HSC,Euclid, LSST...)

We have been monitoring some well-known bright blazars with short LOFAR observations since February 2013 with fortnightly cadence using the full available bandwidth of the High Band Antennas (i.e., 48 MHz centred at 226 MHz). The sources were chosen to be bright at low frequencies and to exhibit strong GHz-frequency radio variability on timescales of weeks to years. None of the five objects selected have been monitored previously in the MHz band. Here we report some preliminary results on flux variability obtained so far with LOFAR. These observations are scientifically valuable in their own right and also act as a proof of principle for broader, higher-cadence monitoring of the extragalactic sky with LOFAR and possibly SKA.

I review the evolution of binary supermassive black holes and focus on the stellar-dynamical mechanisms that may help to overcome the final-parsec problem – the possible stalling of the binary at a separation much larger than is required for an efficient gravitational wave emission. Recent N-body simulations have suggested that a departure from spherical symmetry in the nucleus of the galaxy may keep the rate of interaction of stars with the binary at a high enough level so that the binary continues to shrink rather rapidly. However, a major problem of all these simulations is that they do not probe the regime where collisionless effects are dominant – in other words, the number of particles in the simulation is still not sufficient to reach the asymptotic behavior of the system. I present a novel Monte Carlo method for simulating both collisional and collisionless evolution of non-spherical stellar systems, and apply it for the problem of binary supermassive black hole evolution. I show that in triaxial galaxies the final-parsec problem is largely non-existent, while in the axisymmetric case it seems to still exist in the limit of purely collisionless regime relevant for real galaxies, but disappears in the N-body simulations where the feasible values of N are still too low to get rid of collisional effects.

For proper interpretations of various phenomena in young stars and planetary systems, knowledge of accurate stellar ages is very important. Among a handful of age dating methods commonly used for young (≲500 Myr) stars, lithium depletion boundary (LDB) ages have recently become the most cited and accepted age estimates. However, because of inconsistencies in theoretical evolutionary models, especially for lithium depletion calculations, one has to be cautious in using LDB ages. For a given luminosity, the lithium depletion process is too slow, causing LDB ages to appear older. Various stellar processes affect the surface lithium abundance, and these effects include star spots, accretion history, and magnetic fields. Until we have a self-consistent theoretical evolutionary model for young stars including all relevant stellar effects, caution should be taken when LDB ages are used.

Various programs aimed at exploring the still largely unknown low surface brightness Universe with deep imaging optical surveys have recently started. They open a new window for studies of galaxy evolution, pushing the technique of galactic archeology outside the Local Group (LG). The method, based on the detection and analysis of the diffuse light emitted by collisional debris or extended stellar halos (rather than on stellar counts as done for LG systems), faces however a number of technical difficulties, like the contamination of the images by reflection halos and Galactic cirrus. I review here the on-going efforts to address them and highlight the preliminary promising results obtained with a systematic survey with MegaCam on the CFHT of nearby massive early-type galaxies done as part of the ATLAS3D, NGVS and MATLAS collaborations.

The formation and evolution of Solar System small bodies, in particular those in near-Earth orbits, is a complex problem which solution strongly depends on a better knowledge of their physical properties. To contribute to the international efforts in this direction the IMPACTON project (www.on.br/IMPACTON) set up a dedicated facility denominated Observatório Astronômico do Sertão de Itaparica (OASI). Using the 1-m telescope several dozens of NEAs were observed between March 2012 and October 2014. Here we will present the results obtained for 8 objects. Relative magnitudes were used to obtain lightcurves and derive rotational periods. Applying the inversion method developed by Kaasalainen and Torppa (2001) and Kaasalainen et al. (2001), along with lightcurves from literature, allowed to refine the rotational period of these asteroids as well as to derive their pole direction and shape. The obtained results confirm a lack of poles toward the ecliptic and with a majority of retrograde rotators. A more representative sample, however, is needed in order to drive robust conclusions.

We study the effects of including binary star evolution in population synthesis models. We use the Hurley et al. (2002) code to compute binary star evolutionary tracks, and follow the procedure by Han et al. (2002), in particular, the two 2HeWD merger channel, to form EHB stars from a binary pair. We apply the resulting models to study UV excess ETGs.

Current and forthcoming cosmological data analyses share the challenge of huge datasets alongside increasingly tight requirements on the precision and accuracy of extracted cosmological parameters. The community is becoming increasingly aware that these requirements not only apply to the central values of parameters but, equally important, also to the error bars. Due to non-linear effects in the astrophysics, the instrument, and the analysis pipeline, data covariance matrices are usually not well known a priori and need to be estimated from the data itself, or from suites of large simulations. In either case, the finite number of realisations available to determine data covariances introduces significant biases and additional variance in the errors on cosmological parameters in a standard likelihood analysis. Here, we review recent work on quantifying these biases and additional variances and discuss approaches to remedy these effects.

This is a review of the extant literature and recent work on the scaling relation(s) that link the gas content of galaxies to the measured star formation rates. A diverse array of observing techniques and underlying physical assumptions characterize the determination of these relations at different scales, that range from the tens of parsec sizes of molecular clouds to the tens of kpc sizes of whole galaxies. Different techniques and measurements, and a variety of strategies, have been used by many authors to compare the scaling relations, both within and across galaxies. Although the picture is far from final, the past decade has seen tremendous progress in this field, and more progress is expected over the next several years.

The linear polarization in spectral lines produced by coherent scattering is significantly modified by the quantum interference between the atomic states in the presence of a magnetic field. When magnetic fields produce a splitting which is of the order of or greater than the fine or hyperfine structure splittings, we enter the Paschen-Back effect (PBE) regime, in which the magnetic field dependence of the Zeeman splittings and transition amplitudes becomes non-linear. In general, PBE occurs for sufficiently strong fields when the fine structure states are involved and for weak fields in the case of hyperfine structure states. In this work, we apply the recently developed theory of PBE in the atomic fine and hyperfine structure states including the effects of partial frequency redistribution to the case of Li i 6708 Å doublet. We explore the signatures of PBE in a single scattering event and their applicability to the solar magnetic field diagnostics.

Symmetric and triangle-shaped flux variability in X-ray and gamma-ray light curves is observed from many blazars. We derived the X-ray spectrum changing in time by using a kinetic equation of high energy electrons. Giving linearly changing the injection of low energy electrons into accelerating and emitting region, we obtained the preliminary results that represent the characteristic X-ray variability of the linear flux increase with hardening in the rise phase and the linear decrease with softening in the decay phase.

Triple supermassive black holes (SMBH) can form during the hierarchical mergers of massive galaxies with an existing binary. Perturbations by a third black hole may accelerate the merging process of an inner binary, for example through the Kozai mechanism. We analyze the evolution of simulated hierarchical triple SMBHs in galactic centers, and find resonances in the evolution of the semi-major axis, the eccentricity and the inclination, for both the inner and the outer orbits of the triple system, which are not only Kozai like. Through resonant oscillations, SMBH can trigger a significant increase of the inner SMBH binary eccentricity shortening the merger timescale expected from gravitational wave (GW) emission. As hierarchical triple SMBHs may be frequent in massive galaxies, the influence of orbital resonances is of great importance to our understanding of black hole coalescence and gravitational wave detection. Although Kozai mechanism is believed to play an important role in this process, detailed studies on the pattern of these resonances is necessary.

1. The International Astronomical Union (hereinafter referred to as the Union) is an international nongovernmental organization. Its objective is to promote the science of astronomy in all its aspects.

Variability has now been robustly observed in a range of L and T type field brown dwarfs, primarily at near-IR and mid-IR wavelengths. The probable cause of this variability is surface inhomogeneities in the clouds of these objects, causing a semi-periodic variability signal when combined with the rotational modulation from the 3-12 hour period expected for these objects. Variability at similar or even higher amplitudes may be expected for young brown dwarfs and giant exoplanets, which share similar Teff as field brown dwarfs, but have considerably lower surface gravities. Variability studies of these objects relative to old field objects is then a direct probe of the effects of surface gravity on atmospheric structure. Here I discuss ongoing efforts to detect variability from these young objects, both for free-floating objects and companions to stars, including preliminary results from an ongoing survey of young, low surface gravity objects with NTT SOFI.

We present results on the stellar population properties of massive galaxies at z = 0.7 based on deep, medium-resolution IMACS spectra for a sample of ~ 70 galaxies in the ECDFS with M* > 1010M⊙. The age–mass and stellar metallicity–mass relations for the population as a whole have a similar shape as the local relations over the probed mass range, but offset to ages younger by ~ 4 Gyr and metallicities lower by ~ 0.13 dex. Quiescent galaxies alone have stellar ages and metallicities consistent with passive evolution onto the local quiescent galaxies relations. The evolution in metallicity is driven by star-forming galaxies. However a significant fraction of massive star-forming galaxies have metallicities comparable to those of local quiescent galaxies. If quenched at z < 0.7 they can provide the necessary population to reproduce the scatter in age and metallicity of local quiescent galaxies.