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Nuclear bar catalyzed star formation: (CO)-C-13, (CO)-O-18, and molecular gas properties in the nucleus of Maffei 2

Meier, David S. and Turner, Jean L. and Hurt, Robert L. (2008) Nuclear bar catalyzed star formation: (CO)-C-13, (CO)-O-18, and molecular gas properties in the nucleus of Maffei 2. Astrophysical Journal, 675 (1). pp. 281-302. ISSN 0004-637X. doi:10.1086/524932.

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We present ~3" resolution maps of CO, its isotopologues, and HCN from in the center of Maffei 2. The J = 1-0 rotational lines of 12CO, 13CO, C18O and HCN, and the J = 2-1 lines of 13CO and C18O were observed with the Owens Valley Radio Observatory ( OVRO) and Berkeley-Illinois- Maryland Association (BIMA) arrays. The lower opacity CO isotopologues give more reliable constraints on H-2 column densities and physical conditions than optically thick 12CO. The J = 2-1/1-0 line ratios of the isotopologues constrain the bulk of the molecular gas to originate in low-excitation, subthermal gas. From large velocity gradient (LVG) modeling, we infer that the central giant molecular clouds (GMCs) have nH2 ~10(2.75) cm^(-3) and T-k ~30 K. Continuum emission at 3.4, 2.7, and 1.4 mm was mapped to determine the distribution and amount of H II regions and dust. Column densities derived from C18O and 1.4 mm dust continuum fluxes indicate the standard Galactic conversion factor overestimates the amount of molecular gas in the center of Maffei 2 by factors of ~2-4. Gas morphology and the clear "parallelogram" in the position-velocity diagram shows that molecular gas orbits within the potential of a nuclear (~220 pc) bar. The nuclear bar is distinct from the bar that governs the large-scale morphology of Maffei 2. Giant molecular clouds in the nucleus are nonspherical and have large line widths, due to tidal effects. Dense gas and star formation are concentrated at the sites of the x(1)-x(2)-orbit intersections of the nuclear bar, suggesting that the starburst is dynamically triggered.

Item Type:Article
Related URLs:
URLURL TypeDescription
Meier, David S.0000-0001-9436-9471
Turner, Jean L.0000-0003-4625-2951
Additional Information:© 2008 American Astronomical Society. Received 2007 August 2; accepted 2007 October 28. We are grateful to the faculty and staffs of the Owens Valley Radio Observatory (OVRO) and Berkeley-Illinois-Maryland Association (BIMA) for their support during the observations. We thank the referee, Marshall McCall, for a careful and insightful reading of the paper. D.S.M. acknowledges support from NSF AST 05-06669, the Laboratory for Astronomical Imaging at the University of Illinois (NSF AST 02-28953), and NRAO. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Additional support for this work is provided by NSF grant AST 00-71276 and AST 05-06469 to J.L.T.
Funding AgencyGrant Number
NSFAST 05-06669
NSFAST 02-28953
NSFAST 00-71276
NSFAST 05-06469
National Radio Astronomy ObservatoryUNSPECIFIED
Subject Keywords:galaxies: individual (Maffei 2); galaxies: ISM; galaxies: nuclei; galaxies: starburst; radio lines: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:MEIapj08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12091
Deposited By: Tony Diaz
Deposited On:27 Oct 2008 17:38
Last Modified:08 Nov 2021 22:25

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