CO(J = 1-0) imaging of M51 with CARMA and the Nobeyama 45 m telescope

Jin Koda, Tsuyoshi Sawada, Melvyn C.H. Wright, Peter Teuben, Stuartt A. Corder, Jenny Patience, Nick Scoville, Jennifer Donovan Meyer, Fumi Egusa

Research output: Contribution to journalArticlepeer-review

49 Scopus citations

Abstract

We report the CO(J = 1-0) observations of the Whirlpool Galaxy M51 using both the Combined Array for Research in Millimeter Astronomy (CARMA) and the Nobeyama 45 m telescope (NRO45). We describe a procedure for the combination of interferometer and single-dish data. In particular, we discuss (1) the joint imaging and deconvolution of heterogeneous data, (2) the weighting scheme based on the root-mean-square (rms) noise in the maps, (3) the sensitivity and uv coverage requirements, and (4) the flux recovery of a combined map. We generate visibilities from the single-dish map and calculate the noise of each visibility based on the rms noise. Our weighting scheme, though it is applied to discrete visibilities in this paper, should be applicable to grids in uv space, and this scheme may advance in future software development. For a realistic amount of observing time, the sensitivities of the NRO45 and CARMA visibility data sets are best matched by using the single-dish baselines only up to 4-6 kλ (about 1/4-1/3 of the dish diameter). The synthesized beam size is determined to conserve the flux between the synthesized beam and convolution beam. The superior uv coverage provided by the combination of CARMA long baseline data with 15 antennas and NRO45 short spacing data results in the high image fidelity, which is evidenced by the excellent overlap between even the faint CO emission and dust lanes in an optical Hubble Space Telescope image and polycyclicaromatichydrocarbon emission in a Spitzer 8 μm image. The total molecular gas masses of NGC 5194 and 5195 (d = 8.2 Mpc) are 4.9 × 10 9 M and 7.8 × 107 M , respectively, assuming the CO-to-H2 conversion factor of X CO = 1.8 × 1020 cm-2(K km s-1)-1. The presented images are an indication of the millimeter-wave images that will become standard in the next decade with CARMA and NRO45, and the Atacama Large Millimeter/Submillimeter Array.

Original languageEnglish (US)
Article number19
JournalAstrophysical Journal, Supplement Series
Volume193
Issue number1
DOIs
StatePublished - Mar 2011

Keywords

  • galaxies: individual (NGC 5194, NGC 5195, M51)
  • techniques: image processing
  • techniques: interferometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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