In chemodynamical evolution models it is usually assumed that the Milky Way galaxy forms from the inside-out implying that gas inflows onto the disk decrease with galactocentric distance. Similarly, to reproduce differences between chemical abundances of the thick disk and bulge with respect to those of the thin disk, higher accretion fluxes at early times are postulated. By using a suite of Milky Way-like galaxies extracted from cosmological simulations, we investigate the accretion of gas on the simulated stellar disks during their whole evolution. In general, we find that the picture outlined above holds, although the detailed behavior depends on the assembly history of the Galaxy and the complexities inherent to the physics of galaxy formation.

We re-examined solar polar magnetic fields, using ground based synoptic photospheric magnetograms, during solar cycle 24. IThe signed polar magnetic fields showed an unusual hemispheric asymmetry in the polar field reversal process with a single unambigous reversal in the Southern hemisphere around late 2013 while the polar reversal in the Northern hemisphere started earlier around June 2012, but was completed only by the end of 2014. The examination of the unsigned polar magnetic fields in cycle 24 showed a continuing decline of fields in the Northern hemisphere whereas in the Southern hemisphere, it had partially recovered. However, the overall declining trend in solar polar fields, which began in the mid-1990’s, is still in progress. The continued decline seen in solar photospheric fields raises thequestion of whether we are heading towards a Grand or Maunder like solar minimum.

In this proceeding paper, we introduce the recent results of Galactic maser astrometry by mainly focusing on those obtained with Japanese VLBI array VERA. So far we have obtained parallaxes for 86 sources including preliminary results, and combination with the data obtained with VLBA/BeSSeL provides astrometric results for 159 sources. With these most updated results we conduct preliminary determinations of Galactic fundamental parameters, obtaining R0 = 8.16 ± 0.26 kpc and Θ0 = 237 ± 8 km/s. We also derive the rotation curve of the Milky Way Galaxy and confirm the previous results that the rotation curve is fairly flat between 5 kpc and 16 kpc, while a remarkable deviation is seen toward the Galactic center region. In addition to the results on the Galactic structure, we also present brief overviews on other science topics related to masers conducted with VERA, and also discuss the future prospect of the project.

Methanol is ubiquitous in star-forming regions, and has recently been detected in a protoplanetary disk. Astrochemical models have shown that methanol photolysis contributes to complex organic chemistry in interstellar ices. While some methanol photolysis branching ratios have been measured, infrared condensed-phase measurements rely on assumptions about the chemistry, and mass spectrometric measurements cannot distinguish structural isomers. To address these challenges, we are using pure rotational spectroscopy to quantitatively probe the methanol photolysis products. We use a VUV laser to dissociate methanol in the throat of a supersonic expansion, and probe the products downstream after cooling is complete. We then use a rotational diagram analysis to determine the relative density of each product relative to methanol. We have detected the methoxy, hydroxymethyl, and formaldehyde photolysis products. We present here the experimental setup and the initial results and discuss these results in the context of interstellar chemistry.

The Square Kilometre Array will be an amazing instrument for pulsar astronomy. While the full SKA will be sensitive enough to detect all pulsars in the Galaxy visible from Earth, already with SKA1, pulsar searches will discover enough pulsars to increase the currently known population by a factor of four, no doubt including a range of amazing unknown sources. Real time processing is needed to deal with the 60 PB of pulsar search data collected per day, using a signal processing pipeline required to perform more than 10 POps. Here we present the suggested design of the pulsar search engine for the SKA and discuss challenges and solutions to the pulsar search venture.

IAU Commission 41 (History of Astronomy) was founded in 1948, and between 1991 and its termination in 2015 this Commission hosted seven different Working Groups (one of which was shared with Commission 40 (Radio Astronomy). In this paper we list the objectives of these seven Working Groups and track their progress. We conclude by evaluating the role that each C41 Working Group played in furthering research on the history of astronomy.

We begin with a review of the predictions for cycle 24 before its onset. After summarizing the basics of the flux transport dynamo model, we discuss how this model had been used to make a successful prediction of cycle 24, on the assumption that the irregularities of the solar cycle arise due to the fluctuations in the Babcock–Leighton mechanism. We point out that fluctuations in the meridional circulation can be another cause of irregularities in the cycle.

We address the importance of historical full-disc Ca II K spectroheliograms for solar activity and irradiance reconstruction studies. We review our work on processing such data to enable them to be used in irradiance reconstructions. We also present our preliminary estimates of the plage areas from five of the longest available historical Ca II K archives.

We report astrometric results for seven 6.7 GHz CH3OH and one 22 GHz H2O masers in the Perseus arm with VLBA and VERA observations. Among the eight sources, we succeeded in obtaining trigonometric parallaxes for all sources, except G098.03+1.44 at 6.7 GHz band. By combining our results with previous astrometry results (Choi et al. 2014), we determined an arm width of 0.41 kpc and a pitch angle of 8.2 ± 2.5 deg for the Perseus arm. By using a large sample of the Perseus arm (26 sources), we examined the three-dimensional, non-circular motions (defined as U, V and W) of sources in the Perseus arm as a function of the distance (D) perpendicular to the arm. Interestingly, we found a weighted mean of <U > = 12.7 ± 1.2 km s−1 for 14 sources with D < 0 kpc (i.e. sources on the interior side of the arm) and <U > = −0.3 ± 1.5 km s−1 for 12 sources with D > 0 kpc (i.e. sources exterior to the arm). These findings might be the first observational indication of the ”damping phase of a spiral arm” suggested by the non-steady spiral arm model of Baba et al. (2013). The small pitch angle of the Perseus arm (< 10 deg) also supports the damping phase, based on ”pitch angle vs. arm amplitude” relation shown in Grøsbol et al. (2004).

4MOST is a new wide-field, high-multiplex spectroscopic survey facility for the VISTA telescope of ESO. Starting in 2022, 4MOST will deploy 2400 fibres in a 4.1 square degree field-of-view using a positioner based on the tilting spine principle. In this contribution we give an outline of the major science goals we wish to achieve with 4MOST in the area of Galactic Archeology. The 4MOST Galactic Archeology surveys have been designed to address long-standing and far-reaching problems in Galactic science. They are focused on four major themes: 1) Near-field cosmology tests, 2) Chemo-dynamical characterisation of the major Milky Way stellar components, 3) The Galactic Halo and beyond, and 4) Discovery and characterisation of extremely metal-poor stars. In addition to a top-level description of the Galactic surveys we provide information about how the community will be able to join 4MOST via a call for Public Spectroscopic Surveys that ESO will launch.

The International Astronomical Union was conceived in 1918, and was formed one year later in Brussels. One of the 32 initial Commissions was the Committee on Stellar Photometry that later on became IAU Commission 25 Astronomical Photometry and Polarimetry, and since 2015 Commission B6 with the same name. The initial functions to be exercised by the Committee were

1. (a) to advise in the matter of notation, nomenclature, definitions, conventions, etc., and

2. (b) to plan and execute investigations requiring the cooperation of several observers or institutions.

The basic philosophy was that IAU Commission 25 was to be an advisory body, rather than a decision-making committee that imposes its regulations. This position was reconfirmed at the 10th IAU General Assembly in 1958.

From the early days on, the Commission members engaged in the teaching of the principles of photometric measurement – either via the Commission meetings and the ensuing reports, or via external means, such as lectures and publications. The topics of instruction dealt with absorption of light in the atmosphere, the modification imposed by the character of the receiving apparatus, the unequal response of different receivers to a same stimulus, and variations in the data-recorder response from one experiment to another.

From the 1930s on it was suggested that IAU Commission 25 takes responsibility in matters of standard stars, standard filters and standard calibration methods.

During the first half-century since its foundation, Commission 25 was an active forum for discussions on the basic principles of astronomical photometry, including the associated problems of transformability of magnitudes and colour indices from one instrumental configuration to another. During the second half-century of its existence, the Commission has served as a sort of news agency reporting on the developments in detector engineering, filter technology and data reduction. All along the Commission members were committed to accuracy and precision, a struggle that was primarily driven by the jumps forward in performance and sensitivity of every new detector that was introduced.

The development over one century shows that the Commission was continuously touching on the philosophy of precise measurement, where accurate measuring – for a select group of pioneers – was an end in itself.

This presentation looks back on the opinions of key players in the photometric standardisation debate, and briefly presents two case studies that illustrate the illusionary accuracy reached over a century in determining, as Commission member Ralph Allan Sampson put it, “a detail like magnitude”.

The efficiency of dust formation in a variety of environments is an ongoing topic for discussions, especially if it comes to dust formation in the interstellar medium. Although this possibility is discussed in a wide range of numerical studies, experiments on the formation of dust at low densities and temperatures are mostly lacking. This contribution summarizes the main findings of our low-temperature condensation experiments including the formation of silica, complex silicates with pyroxene and olivine stoichiometry, and of carbonaceous refractory materials. Atomic and molecular species to be expected as products of supernovae shock fronts were produced by laser ablation of silicates and graphite. These species were deposited together with a rare gas on cold substrates representing the surfaces of surviving dust grains in the interstellar medium. After characterizing the precursor species, the rare gas matrix was annealed to induce diffusion and reactions between the initial components. We found the production of amorphous and homogeneous silica and magnesium iron silicates at temperatures of about 12 K in a barrierless reaction as monitored by infrared spectroscopy. The 10 μm band of the low-temperature siliceous condensates shows a striking similarity to the 10 μm band of interstellar silicates. Carbonaceous atoms and molecules can also react without a barrier and form an amorphous or hydrogenated amorphous carbon material. The refractory condensate has properties comparable to fullerene-like carbon grains formed at high temperatures.

We present in this work the development of a solar data assimilation method based on an axisymmetric mean field dynamo model and magnetic surface data. Our mid-term goal is to predict the solar quasi cyclic activity. We focus on the ability of our variational data assimilation algorithm to constrain the deep meridional circulation of the Sun based on solar magnetic observations. Within a given assimilation window, the assimilation procedure minimizes the differences between data and the forecast from the model, by finding an optimal meridional circulation in the convection zone, and an optimal initial magnetic field, via a quasi-Newton algorithm. We demonstrate the capability of the technique to estimate the meridional flow by a closed-loop experiment involving 40 years of synthetic, solar-like data. We show that the method is robust in estimating a (stochastic) time-varying flow fluctuating 30% about the average, and that the horizon of predictability of the method is ~ 1 cycle length.

The MPIfR is working together with SKA-SA and the Universities of Manchester and Oxford to deploy three instruments on MeerKAT: An S-band receiver system, a dedicated beamforming cluster and a flexible pulsar search cluster. Together these instruments will provide MeerKAT with powerful tools for supporting a wide range of scientific applications and in particular will enable large-scale pulsar and fast transient surveys to be performed. In these proceedings we describe the design, implementation and deployment timeline for these instruments.

The Large Synoptic Survey Telescope (LSST) surveys have initially been optimized to omit the inner part of the Milky Way disk/bar from deep and cadence observations. However it is now clear that the LSST will be powerful for Galactic astronomy and may play a crucial role in continuing to extend the Gaia astrometric catalog until a future satellite, either optical or IR, carries on. LSST will provide metallicities and kinematics for the bulge, and will map halo structures to as distant as 450 kpc, nearly half the distance to the Andromeda galaxy. Thanks to the unprecedented calibration effort for its photometric system, and surprisingly good astrometry (transverse velocity measurements of 0.2 mas/yr at r=21; 1 mas/yr at r=24) LSST will provide photometric abundances and distance constraints for a billion or more Milky Way stars to distances of 450 kpc, and kinematics from proper motions to ~100 kpc. Single observation depths reach ~24 in the ugrizy bands, while depths at end of mission reach ~27. Although halo structures such as streams and dwarf galaxies are initially identified by the RR Lyrae and giants, their structure will be fleshed out by the 100× more abundant dwarfs that will be detected to 100 kpc (single observation) and ~300 kpc by end of mission. More complete mapping of stream structures may constrain the mass distribution of dark matter and perhaps confirm the interaction of dark matter halos and streams. I also describe the Blanco DECam Bulge Survey, a 200 deg2 LSST pathfinder survey of the bulge in ugrizy using the Dark Energy Camera on the Blanco 4m telescope. The purpose of this article is to encourage active workers on the Milky Way and Local Volume to participate in the LSST project, in particular to urge that the Galactic Plane receive the same cadence and depth coverage as the rest of the extragalactic sky.

A series of catalytic reactions has been performed in our laboratory using olivine-type silicates (OTS) and SiC as catalysts for the conversion of carbon-containing molecules (such as acetylene, CO and methanol) to small organic molecules (C2H4, C3H3, CH3O) and also polycyclic aromatic hydrocarbons (PAHs). Experimentally, small-to-medium-sized gas-phase compounds such as PAHs, reaction intermediates and hydrocarbon compounds were detected in situ using the time-of-light mass-spectrometry technique. Solid deposition on the catalyst surface was examined by high-resolution transmission electron microscopy and thermo-gravimetric analysis techniques. Our laboratory results show that the conversion of acetylene to PAHs, the CO disproportionation reaction for producing CO2 and carbon deposition (graphitic and carbon nanostructures), and also the transformation of methanol to hydrocarbon compounds can easily be achieved with OTS as a catalyst. Furthermore, the conversion of acetylene to PAHs could also be achieved by SiC as the catalyst. It is proposed that these catalytic reactions mimic similar chemical processes in circumstellar envelopes (CSEs).

The founding and development of two commissions of the IAU that played a unique role in IAU history are traced. Commission 38 for the Exchange of astronomers was founded in 1946 with Frederick Stratton as first president, and it expended funds (initially granted by UNESCO) for astronomers to travel on exchange visits. Commission 46 for the Teaching of astronomy was founded in 1964 with Evry Schatzmann as first president. This was a time of rapidly growing interest in the IAU for teaching astronomy and in due course for promoting astronomy in developing countries. For a while, both commissions operated under the wing of the Executive Committee. Their role was unique as they were the only IAU commissions to have their own budget, as well as aspiring to bring about social change in the astronomical community. By 2000 both commissions merged into C46 (Astronomy education and development) and by that time various programmes such as the International School for Young Astronomers (ISYA), the working group World-wide Development of Astronomy (WWDA) and the working group Teaching Astronomy for Development (TAD), which grew out of the Visiting Lecturers’ Program (VLP), were all run by C46. When the IAU established the Office of Astronomy for Development in 2011, many of these functions were removed from the commission and in any case C46 ceased to exist in 2015 when all the old commissions were disestablished. In 2015 the Office for Young Astronomers took over the running of the ISYA. The history of C38 and C46 represents a time of active change in the way the IAU was engaging with people. It was more than just a union for scientific research, but in the world of scientific unions, it was remarkable for taking an active hands-on role in implementing social change. In the history of these two commissions, the Swiss astronomer Edith Müller played a leading dynamic role. She served as president of C46 (1967-73), of C38 (1985-88) as well as IAU General Secretary (1976-79).

Preliminary results of distinguishing solar filaments on daily observation data at the Hα spectral line of the Kodaikanal Solar Observatory (1912-2002) are presented.

To distinguish the boundaries of solar filaments, methods have been developed, based on automatic procedures for distinguishing low-contrast objects on the solar disk as well as on editing the boundaries of selected structures in semi-automatic mode. An analysis of solar filaments’ characteristics has been performed. We are considered variation of the average tilt-angle and the radius of curvature of the filaments in 15-23 cycles of activity.

Sunspot observations and counting are carried out at the Specola Solare Ticinese in Locarno since 1957 when it was built as an external observing station of the Zurich observatory. When in 1980 the data center responsibility was transferred from ETH Zurich to the Royal Observatory of Belgium in Brussels, the observations in Locarno continued and Specola Solare Ticinese got the role of pilot station. The data collected at Specola cover now the last 6 solar cycles.

The aim of this presentation is to discuss and give an overview about the Specola data collection, the applied counting method and the future archiving projects. The latter includes the publication of all data and drawings in digital form in collaboration with the ETH Zurich University Archives, where a parallel digitization project is ongoing for the document of the former Swiss Federal Observatory in Zurich collected since the time of Rudolph Wolf.

The Galactic Center contains large amounts of molecular and ionized gas as well as a plethora of energetic objects. Water masers are an extinction-insensitive probe for star formation and thus ideal for studies of star formation stages in this highly obscured region. With the Australia Telescope Compact Array, we observed 22 GHz water masers in the entire Central Molecular Zone with sub-parsec resolution as part of the large SWAG survey: “Survey of Water and Ammonia in the Galactic Center”. We detect of order 600 22 GHz masers with isotropic luminosities down to ~10−7 L⊙. Masers with luminosities of ≳10−6 L⊙ are likely associated with young stellar objects. They appear to be close to molecular gas streamers and may be due to star formation events that are triggered at pericenter passages near Sgr A*. Weaker masers are more widely distributed and frequently show double line features, a tell-tale sign for an origin in evolved star envelopes.