High Resolution BIMA Observations of CO, HCN, and 13CO in NGC 1068

We present high-resolution CO, HCN, and 13CO maps of the inner arcminute of NGC 1068 made with the BIMA interferometer. Several features appear in the CO map which have not previously been observed: (1) a firm detection of CO line emission from a compact region centered on the nucleus of the galaxy; (2) the detection of a triplet velocity structure characteristic of kinematically independent regions shown on the spectrum of the unresolved nuclear emission ; and (3) the detection of a molecular bar, the extent and position angle of which are in good agreement with the 2 $\mu$m stellar bar. The most intense CO emission is nonnuclear; the structure and kinematics of this emission imply that this gas is distributed along the inner spiral arms and not in a ring. The bar's kinematic influence on the molecular gas in the spiral arms is modest, with typical ordered noncircular motions of \la\ 30 \kms\ in the plane of the galaxy. Interior to the spiral arms, the bar's influence is more dramatic, as reflected by the twisted isovelocity contours in the CO and HCN velocity fields. The surface density of molecular gas within the central 100 pc radius of NGC 1068 is the same as that in the central 200 pc radius in the Milky Way to within the uncertainties. There is evidence for an $m= 1$ kinematic mode in NGC 1068; we find the kinematic center of rotation to be displaced from the radio continuum center by about 2.9", or 200 pc. The HCN image, in contrast to the CO map, shows a strong concentration of emission centered on the nucleus. The ratio of integrated intensities of the HCN emission to that of CO is about 0.6 and is the highest ratio measured in the central region of any galaxy.Comment: 35 pages of uuencoded, compressed postscript, 20 postscript figures not included but available from [email protected] or from ftp://astro.astro.umd.edu/pub/thelfer/n1068_figs.ps.Z To appear in The Astrophysical Journal, V. 450, Sept. 199

Dense Gas in the Milky Way

We present a study of dense gas emission in the Milky Way in order to serve as a basis for comparison with extragalactic results. This study combines new observations of HCN, CS, and CO in individual GMCs and in the Milky Way plane with published studies of emission from these molecules in the inner 500 pc of the Milky Way. We find a strong trend in the fraction of emission from dense gas tracers as a function of location in the Milky Way: in the bulge, I_{HCN}/I_{CO} = 0.081 \pm 0.004, in the plane, I_{HCN}/I_{CO} = 0.026 \pm 0.008 on average, and over the full extent of nearby GMCs, I_{HCN}/I_{CO} = 0.014 \pm 0.020. Similar trends are seen in I_{CS}/I_{CO}. The low intensities of the HCN and CS emission in the plane suggests that these lines are produced by gas at moderate densities; they are thus not like the emission produced by the dense, pc-scale star forming cores in nearby GMCs. The contrast between the bulge and disk ratios in the Milky Way is likely to be caused by a combination of higher kinetic temperatures as well as a higher dense gas fraction in the bulge of the Milky Way.Comment: 34 pages LaTeX, AASTEX macros, includes 11 postscript figures. To appear in ApJ 478, March 199

The BIMA Survey of Nearby Galaxies (BIMA SONG). II. The CO Data

The BIMA Survey of Nearby Galaxies is a systematic imaging study of the 3 mm CO J = 1--0 molecular emission within the centers and disks of 44 nearby spiral galaxies. The typical spatial resolution of the survey is 6", or 360 pc at the average distance (12 Mpc) of the sample, over a field of view of 10kpc. The velocity resolution of the CO observations is 4 km/s. The sample was not chosen based on CO or infrared brightness; instead, all spirals were included that met the selection criteria of vsun = -20deg, inc <= 70deg, D25 < 70', and BT < 11.0. The detection rate was 41/44 sources or 93%. Fully-sampled single-dish CO data were incorporated into the maps for 24 galaxies; these single-dish data comprise the most extensive collection of fully-sampled, two-dimensional single-dish CO maps of external galaxies to date. We also tabulate direct measurements of the global CO flux densities for these 24 sources. We demonstrate that the measured ratios of flux density recovered are a function of the signal-to-noise of the interferometric data. We examine the degree of central peakedness of the molecular surface density distributions and show that the distributions exhibit their brightest CO emission within the central 6" in only 20/44 or 45% of the sample. We show that all three Local Group spiral galaxies have CO morphologies that are represented in SONG, though the Milky Way CO luminosity is somewhat below the SONG average, and M31 and M33 are well below average. This survey provides a unique public database of integrated intensity maps, channel maps, spectra, and velocity fields of molecular emission in nearby galaxies.Comment: Full-color reprints available from the authors; full resolution figures also available in electronic version of published article or at http://astro.berkeley.edu/~thelfer/bimasong_supplement.pd

ALMA Project Book, Chapter 15: Array Configuration

this document. However, to give the reader a feel for the arrays that the Keto and Kogan algorithms produce, we present sample configurations in Figures 15.1 through 15.6. Figure 15.1: Sample Keto array snapshot at 230 GHz. (left) Antenna locations in meters, (middle) snapshot (u,v) coverage, and (right) the resulting synthesized beam, with contours are at 10, 20, 40, 60, 80, 100%. Note the large inner sidelobes. Figure 15.2: Sample 3 km array track for a Keto 20-element array optimized for 4-hour tracks (Holdaway, Foster, &amp; Morita 1996), at 230 GHz. The contours are 0.05, 0.10, 0.15, 0.20, 0.40, 0.60, 0.80, 1.0. The outer sidelobes are reduced for long tracks, but the inner sidelobes remain high. Figure 15.3: Sample compact array pad positions are plotted in diamonds on the left panel along with the zenith snapshot uv coverage. The resulting naturally weighted dirty beam is shown on the right. The greyscale is between-0.05 and +0.10, and the largest sidelobe inside the primary beam is about 5%. Figure 15.4: Sample Kogan 3 km array pad positions are plotted in diamonds on the left panel along with the zenith snapshot uv coverage. The resulting naturally weighted dirty beam is shown on the right. The greyscale is between-0.05 and +0.10, and the largest sidelobe inside the primary beam is about 10%. Figure 15.5: The array and zenith uv coverage for the &apos;zoom spiral&apos; array concept proposed by Conway (1998 and 2000a). Open circles are unoccupied pads and filled symbols are antennas. The top row shows the largest configuration, most antennas lie on the outer ring and so the resolution is maximized. The bottom row shows the array and uv coverage after moving inward approximately half of the antennas. The uv coverage is now centrally condensed and close to gaussian distributed..