DivH: Interstellar Matter & Local Universe

NGC3532 eso1439a

The MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile captured this richly colourful view of the bright star cluster NGC 3532 in Carina. Some of the stars still shine with a hot bluish colour, but many of the more massive ones have become red giants and glow with a rich orange hue.
(ESO / G. Beccari)

Division H, Interstellar Matter and Local Universe, covers a wide range of topics, including the structure, content, chemistry, radiation and dynamics of gas and dust, plus star-forming regions, stellar clusters, the Milky Way and other local galaxies. There is considerable overlap with nearly every other IAU Division because the Milky Way often contains the best examples of objects and phenomena that are studied more specifically elsewhere.

Division H has sole “ownership” of three Commissions: Local Universe (H1; Eva Grebel, President), Astrochemistry (H2; Thomas Millar) and Planetary Nebulae (H3; Letizia Stanghellini). It is the primary parent of one Inter-Division Commission — Stellar Clusters Throughout Cosmic Space and Time (H4; Richard de Grijs) — and partners in two more Inter-Division Commissions for which Division J (Galaxies and Cosmology) serves as parent: Galaxy Spectral Energy Distributions (J1; Denis Burgarella) and Intergalactic Medium (J2; Avery Meiksin). Division H has one Working Group, The Galactic Center (Cornelia Lang), which unites the many groups and observing programs that study our Milky Way’s supermassive black hole and central molecular zone.

Our Division Days meeting on Friday and Monday, August 24th and 27th, begins with summaries of the three Symposia held during the first week of the General Assembly, with invited speakers who were organizers of those Symposia. It includes invited talks by the four 2017 and 2018 IAU PhD Prize winners in our Division, namely Yang Huang, Gina Panopoulou, Long Wang and Siyao Xu, plus 19 invited talks on essentially all of the main Division H topics. There will also be business meetings for the Division, Commissions and Working Groups, as well as numerous poster presentations.

Gaia Sky

Plotted in galactic coordinates, with the plane of the Milky Way stretching across the middle, this image shows 1.7 billion stars and a handful of Local Group galaxies as mapped by the European Space Agency’s Gaia satellite. (ESA / Gaia / DPAC)

Commission H1 & Division Days

Commission H1 concentrates on the Milky Way and surrounding galaxies, studying the distribution of stellar ages, chemical abundances and kinematics to understand the assembly and evolution of our galaxy and its neighbors. It typically resolves individual stellar populations and maps dust and interstellar matter with cloud-scale resolution. The recent Gaia satellite catalog of 1.7 billion stars will have a major impact in this field. Other efforts search for high-energy sources and dark-matter signals from nearby dwarf galaxies. Computer simulations including cosmological and chemodynamical evolution with dark matter and baryons are approaching the resolution required to model disk and dwarf galaxies realistically.

Many talks at our Division Days meeting, particularly on Monday, August 27th, cover topics from Commission H1. They include reviews of the thick disk, the bar and bulge concentration and the Galactic Centre in the Milky Way, as well as reviews of the neighboring Large and Small Magellanic Clouds, the Magellanic Stream, other Local Group dwarf galaxies, as well as the circumgalactic medium around the Milky Way and the Andromeda Galaxy, M31. In the context of age-dating Milky Way stars, the relatively new field of asteroseismology for red giants will also be covered by an invited talk, as it opens the way to measure precise ages for very distant field stars. One of the first talks on Friday, 24 August, will be a review of Symposium 344 on dwarf galaxies. A PhD Prize talk on galactic stellar kinematics will also take place Friday morning.

Division Days will also present invited reviews on interstellar dust and interstellar turbulence, including a PhD Prize talk on turbulence and another on interstellar filaments and magnetic fields. Galaxy-wide studies of interstellar matter will be covered in an invited talk on the Local Group spiral galaxy M33 and in another talk on molecules in nearby galaxies as seen by ALMA.

Planetary nebula

Molecular hydrogen gas in the planetary nebula NGC 2346 in Monoceros, viewed with the highest angular resolution for a planetary nebula to date thanks to the GeMS/GSAOI multi-conjugate adaptive optics system. The image is about 1 arc minute on a side; north is up and east to the left. (Gemini Observatory / AURA)

HLTauri alma and model

Observations (left) and model (right) of the nearby planet-forming disk HL Tauri. The image was featured on NASA’s Astronomy Picture of the Day website on November 10, 2014. (Observations: ALMA (ESO / NAOJ / NRAO) / NSF; model: Carlos Tapia & Susana Lizano / UNAM, Mexico)

Commissions H2, H3, H4 & Division Days

Commission H2 on astrochemistry has connections with many other branches of astronomy and laboratory physics, including physical chemistry, spectroscopy and astrobiology, along with exoplanet characterization, which has strong connections with astrophysical chemistry. H2 started an Inter-Commission Working Group, Education and Training in Astrobiology, which produces massive open online courses (MOOCs), collects recorded lectures and conferences in astrobiology going back a decade and provides outreach to high-school teachers and the general public. The group started an annual astrobiology training school and runs a two-day training workshop at major conferences. Two lectures at Division Days will be about astrochemistry, and a third will be about the chemistry of protostellar cores and disks.

Commission H3 studies the observation and theory of planetary nebulae. There is one talk at Division Days summarizing the main results of IAU Symposium 343 on asymptotic giant branch stars. AGB stars and planetary nebulae are important sources of chemical enrichment in galaxies and perhaps also in star clusters. The also serve as tracers of stellar evolution that can be observed at great distances because of their intrinsic brightness and concentrated line emission.

Commission H4 concerns itself with star clusters throughout cosmic space and time. It includes the observation and theory of stellar groupings as they form, evolve and disrupt, as well as star formation, stellar feedback and stellar interactions in various environments. At the Division Days meeting on Monday, 27 August, the first talk will summarize the previous week’s Symposium 345 on cosmic origins, which includes a major component about the formation of the solar system and its likely early clustered environment. Four other talks will be about star formation or stellar clusters, and one of the PhD Prize talks is about the largest simulation ever run for the evolution of a massive star cluster.

BRUCE ELMEGREEN is President of Division H. He does research on stellar and star-cluster formation and galactic structure and is a staff member of the IBM Research Division in Yorktown Heights, New York.