Session A1: The Local Group and Beyond: New Windows on Star Formation and Galaxy Evolution

APOGEE: A New Look at the Structure, Dynamics and Evolution of the Milky Way

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a large-scale, systematic and homogeneous spectroscopic census of the the stellar populations of the Milky Way. Because it samples stellar spectra at infrared wavelengths (from 1.51-1.68 μm), APOGEE is able to peer through the veils of dust that obscure and hinder traditional optical wavelength surveys to create the most comprehensive spectroscopic probe of all parts of our home Galaxy. Moreover, because the APOGEE spectra are of high resolution ($\lambda/\Delta\lambda \sim 22,500$) with high $S/N$ and include time series information via repeat visits to stars, this database is being applied to numerous, wide-ranging problems in Galactic astronomy, stellar populations, stellar astrophysics and even the study of exoplanets. Operating from 2011-2014 as part of the Sloan Digital Sky Survey III (SDSS-III), and now continuing as ``APOGEE-2’’ in SDSS-IV, the APOGEE project has already amassed over a million spectra from its northern spectrograph attached to the Sloan 2.5-m Telescope at APO in New Mexico, and will soon begin collecting data for stars in the Southern Hemisphere with a twin spectrograph attached to the du Pont 2.5-m Telescope in Chile. I will summarize some science highlights from the APOGEE project, including measurements of Galactic dynamics, age and multi-element atomic composition maps for stars across the Galaxy, and the discovery and characterization of substellar mass companions and rare species of stars.   

High Resolution Studies of Star Formation in the Milky Way

Stars are formed through the interactions of gravity, turbulent gas motions, magnetic fields, and feedback from previous generations of stars. Observations of nearby star forming molecular clouds in the Milky Way allow us to study these physical processes at scales that cannot be resolved in other galaxies. In this talk I will discuss recent advances in our understanding of local star formation through large area detailed mapping of thermal dust emission from the BLAST balloon-borne telescope and the Herschel Space Observatory. These observations have shown that the morphology of star forming regions is dominated by filamentary structures, and that the densest filaments seem to be preferential sites of star formation. I will also show how measurements of the polarization of thermal dust emission from a new generation of submillimeter polarimeters have been used to create highly detailed maps of magnetic fields in molecular clouds. The resulting maps provide insight into the role played by magnetic fields in the star formation process.   

Probing Extreme Star Formation in the Local Universe with ALMA

Star formation is arguably one of the most fundamental physical processes in determining the properties of the visible universe. Observationally constraining the physical conditions that gave rise to different modes of star formation has been long-standing challenge. Now with the ALMA Observatory on-line, we can begin to probe the birth environments of massive clusters in a variety of "local" galaxies with sufficient angular resolution. I will give an overview of ALMA observations of galaxies in which candidate proto-globular cluster molecular clouds have been identified. These new data probe the physical conditions that give rise to globular clusters, providing information on their densities, pressures, and temperatures. In particular, the observations indicate that these clouds may be subject to external pressures of P/k $> 10^8$ K cm$^{-3}$, which is consistent with the prevalence of optically observed adolescent super star clusters in interacting galaxy systems and other high pressure environments. ALMA observations also enable an assessment of the molecular cloud chemical abundances in the regions surrounding infant globular clusters. Molecular clouds associated with these clusters are strongly correlated with HCO+ emission, but appear to have relatively low ratio of CO/HCO+ emission compared to other clouds, indicating that the star clusters are impacting the molecular abundances in their vicinity.   

High redshift star formation and the assembly of the Hubble sequence

The assembly and evolution of galaxies across cosmic history can provide stringent tests of several fundamental physical parameters, including the nature of the dark matter quantum and the equation of state of dark energy. The last decade has been an exciting time for studies of galaxy assembly; observations have used both large-scale surveys and detailed studies of individual systems to measure the redshift evolution of star formation rates and black hole accretion, while hydrodynamical simulations can reproduce the statistical properties of observed galaxies and are starting to reproduce their internal structures. There remain however a number of fundamental open questions, including the physical mechanisms by which free gas is converted into stars and central black holes, the ways in which star formation and black hole accretion may affect each other, and the relevance of taxonomic structures such as spiral arms and bars. In this talk I will review the key advances made over the last decade in understanding galaxy assembly across the history of the Universe, and discuss some of the most insightful routes forward for studies of galaxy assembly over the next decade.