We have mapped the central region of NGC 4945 in the J = 2 → 1 transition of 12 CO, 13 CO, and C 18 O, as well as the continuum at 1.3 mm, at an angular resolution of 5 ′′ × 3 ′′ with the Submillimeter Array. The relative proximity of NGC 4945 (distance of only 3.8 Mpc) permits a detailed study of the circumnuclear molecular gas and dust in a galaxy exhibiting both an AGN (classified as a Seyfert 2) and a circumnuclear starburst in an inclined ring with radius ∼2. ′′ 5 (∼50 pc). We infer the systemic velocity ∼585 km s −1 from channel maps and PV-diagrams. We find that all three molecular lines trace an inclined rotating disk with major axis aligned with that of the starburst ring and large-scale galactic disk, and which exhibits solid-body rotation within a radius of ∼5 ′′ (∼95 pc). The rotation curve flattens beyond this radius, and the isovelocity contours exhibit an S-shaped asymmetry suggestive of a highly inclined bar as has been invoked to produce a similar asymmetry observed on larger scales. We infer an inclination for the nuclear disk of 62 • ±2 • , somewhat smaller than the inclination of the large-scale galactic disk of ∼78 • . The continuum emission at 1.3 mm also extends beyond the starburst ring, and is dominated by thermal emission from dust. If it traces the same dust emitting in the far-infrared, then the bulk of this dust must be heated by star-formation activity rather than the AGN. We discover a kinematically-decoupled component at the center of the disk with a radius smaller than 1. ′′ 4 (27 pc), but which spans approximately the same range of velocities as the surrounding disk. This component has a higher density than its surroundings, and is a promising candidate for the circumnuclear molecular torus invoked by AGN unification models.

We have used the Submillimeter Array (SMA) to make the first interferometric observations (beam size ∼ 1 or ∼ 400 pc) of the 12 CO J = 6 − 5 line and 435 μm (690 GHz) continuum emission toward the central region (half power field of view 17 ) of the nearby ultra-luminous infrared galaxy (ULIRG) Arp 220. These observations resolve the eastern and western nuclei from each other, in both the molecular line and dust continuum emission. At 435 μm, the peak intensity of the western nucleus is stronger than the eastern nucleus, and the difference in peak intensities is less than at longer wavelengths. Fitting a simple model to the dust emission observed between 1.3 mm and 435 μm suggests that dust emissivity power law index in the western nucleus is near unity and steeper in the eastern nucleus, about 2, and that the dust emission is optically thick at the shorter wavelength. Comparison with single dish measurements indicate that the interferometer observations are missing ∼ 60% of the dust emission, most likely from a spatially extended component to which these observations are not sensitive. The 12 CO J = 6 − 5 line observations clearly resolve kinematically the two nuclei. The distribution and kinematics of the 12 CO J = 6 − 5 line appear to be very similar to lower J CO lies observed at similar resolution. Analysis of multiple 12 CO line intensities indicates that the molecular gas in both nuclei have similar excitation conditions, although the western nucleus is warmer and denser. The excitation conditions are similar to those found in other extreme environments, including the nearby starburst galaxy M82, the active galactic nucleus (AGN) hosting ULIRG Mrk 231, and the high-z QSO BR 1202-0725. Simultaneous lower resolution observations of the 12 CO, 13 CO, and C 18 O J = 2 − 1 lines show that the 13 CO and C 18 O lines have similar intensities, which suggests that both of these lines are optically thick, or possibly that extreme high mass star formation has produced in an overabundance of C 18 O.

We present a study of the largest available sample of near-infrared selected (i.e., stellar mass selected) dynamically close pairs of galaxies at low redshifts (z < 0.3). We combine this sample with new estimates of the major-merger pair fraction for stellar mass selected galaxies at z < 0.8, from the Red Sequence Cluster Survey (RCS1). We construct our low-redshift K−band selected sample using photometry from the UKIRT Infrared Deep Sky Survey (UKIDSS) and the Two Micron All Sky Survey (2MASS) in the K−band (∼ 2.2 µm). Combined with all available spectroscopy, our K−band selected sample contains ∼ 250, 000 galaxies and is > 90% spectroscopically complete. The depth and large volume of this sample allow us to investigate the low-redshift pair fraction and merger rate of galaxies over a wide range in K−band luminosity. We find the major-merger pair fraction to be flat at ∼ 2% as a function of K−band luminosity for galaxies in the range 10 8 − 10 12 L ⊙ , in contrast to recent results from studies in the local group that find a substantially higher low-mass pair fraction. This low-redshift major-merger pair fraction is ∼ 40 − 50% higher than previous estimates drawn from K−band samples, which were based on 2MASS photometry alone. Combining with the RCS1 sample we find a much flatter evolution (m = 0.7 ± 0.1), in the relation f pair ∝ (1 + z) m , than indicated in many previous studies. These results indicate that a typical L ∼ L * galaxy has undergone ∼ 0.2 − 0.8 major mergers since z = 1 (depending on the assumptions of merger timescale and percentage of pairs that actually merge).

PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ∼1.6−2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project is now going into the construction phase aiming at undertaking system integration in 2017-2018 and subsequently carrying out engineering operations in 2018-2019. This article gives an overview of the instrument, current project status and future paths forward.