Superconducting quantum detectors

Abstract:

We used Spitzer Space Telescope 3.6, 8.0, 70 and 160 μm data, James Clerk Maxwell Telescope HARP-B CO J = (3-2) data, National Radio Astronomy Observatory 12 m telescope CO J= (1-0) data and Very Large Array H i data to investigate the relations among polycyclic aromatic hydrocarbons (PAHs), cold (∼20 K) dust, molecular gas and atomic gas within NGC 2403, an SABcd galaxy at a distance of 3.13 Mpc. The dust surface density is mainly a function of the total (atomic and molecular) gas surface density and galactocentric radius. The gas-to-dust ratio monotonically increases with radius, arying from ∼100 in the nucleus to ∼400 at 5.5 kpc. The slope of the gas-to-dust ratio is close to that of the oxygen abundance, suggesting that metallicity strongly affects the gas-to-dust ratio within this galaxy. The exponential scale length of the radial profile for the CO J = (3-2) emission is statistically identical to the scale length for the stellar continuum-subtracted 8 μm (PAH 8 μm) emission. However, CO J equals; (3-2) and PAH 8 μm surface brightnesses appear uncorrelated when examining sub-kpc-sized regions. © 2010 The Authors. Journal compilation © 2010 RAS.

Abstract:

We present the results of large-area ¹²COJ = 3-2 emission mapping of three nearby field galaxies, NGC628, NGC3521, and NGC3627, completed at the James Clerk Maxwell Telescope as part of the Nearby Galaxies Legacy Survey. These galaxies all have moderate to strong ¹²COJ = 3-2 detections over large areas of the fields observed by the survey, showing resolved structure and dynamics in their warm/dense molecular gas disks. All three galaxies were part of the Spitzer Infrared Nearby Galaxies Survey sample, and as such have excellent published multiwavelength ancillary data. These data sets allow us to examine the star formation properties, gas content, and dynamics of these galaxies on sub-kiloparsec scales. We find that the global gas depletion time for dense/warm molecular gas in these galaxies is consistent with other results for nearby spiral galaxies, indicating this may be independent of galaxy properties such as structures, gas compositions, and environments. Similar to the results from The H I Nearby Galaxy Survey, we do not see a correlation of the star formation efficiency with the gas surface density consistent with the Schmidt-Kennicutt law. Finally, we find that the star formation efficiency of the dense molecular gas traced by ¹²COJ = 3-2 is potentially flat or slightly declining as a function of molecular gas density, the ¹²COJ = 3-2/J = 1-0 ratio (in contrast to the correlation found in a previous study into the starburst galaxy M83), and the fraction of total gas in molecular form. © 2010. The American Astronomical Society. All rights reserved.