Molecular Gas in Candidate Double Barred Galaxies I. The Diverse Morphology and Dynamics of NGC 2273 and NGC 5728

Abstract

Double bars have been proposed as a means of transporting molecular gas past inner Lindblad resonances into the nuclear regions, where it can fuel active or starburst nuclei. Thus far, the existence of double bars has been determined predominantly through analysis of near infrared images, which can tell us little about the dynamics and inflow rates of these systems. We have observed two double bar galaxy candidates (NGC 2273 and NGC 5728) in CO J=1-0 with the Owens Valley Radio Observatory Millimeter Array. Despite the similarity in the near infrared images of these galaxies, we see rather different nuclear morphologies in the CO maps. NGC 2273 shows evidence of a nuclear gas bar, aligned with the nuclear stellar bar seen in the near infrared images. Both the nuclear gaseous and stellar bars are misaligned from the large scale bar by approximately 90 degrees, which also allows the possibility that both are the result of stars and gas populating the $x_2$ orbits of the primary bar. Estimates using dynamical friction arguments and star formation rates suggest significant gas inflow rates along the nuclear bar of NGC 2273. Conversely, NGC 5728 does not show any evidence for a nuclear molecular bar, but shows an arc of CO clumps that peaks just to the south-west of the dynamical center and curves to the south-east where it follows the dust lane to the south. Models of double-barred galaxies suggest that these galaxies should contain large amounts of molecular gas in their nuclei. Our calculations suggest that both galaxies contain sufficient amounts of gas in their nuclei, but only NGC 2273 shows evidence for a nuclear gas bar. This may be the result of past episodes of star formation exhausting and dispersing the nuclear gas of NGC 5728, but is more likely evidence that NGC 5728 has undergone a minor merger event.

26 pages + 8 figures, to appear in the Aug 20, 2002 issue of ApJ

References in corpus (6)

• Bar-driven Transport of Molecular Gas to Galactic Centers and Its Consequences
• Molecular Gas, Dust and Star Formation in the Barred Spiral NGC 5383
• Orbits Supporting Bars within Bars
• A gas-rich nuclear bar fuelling a powerful central starburst in NGC 2782
• Non-circular Gas Kinematics and Star Formation in the Ringed Galaxy NGC 4736
• A counterrotating central component in NGC 5728

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• The multiphase gas structure and kinematics in the circumnuclear region of NGC 5728
• The Self-Regulated Growth of Supermassive Black Holes
• Extragalactic H_2O masers and X-ray absorbing column densities
• Radial Gas Flows in Colliding Galaxies: Connecting Simulations and Observations
• Structure and kinematics of candidate double-barred galaxies
• The Black Hole - Bulge Mass Relation in Megamaser Host Galaxies
• Long-Lived Double-Barred Galaxies From Pseudo-Bulges
• Clocking the assembly of double-barred galaxies with the MUSE TIMER project
• GATOS: missing molecular gas in the outflow of NGC5728 revealed by JWST
• Observable Properties of Double-Barred Galaxies in N-Body Simulations
• Using Megamaser Disks to Probe Black Hole Accretion
• Searching for molecular gas in/outflows in the nuclear regions of five Seyfert galaxies
• Molecular Gas in Candidate Double-Barred Galaxies II. Cooler, Less Dense Gas Associated with Stronger Central Concentrations
• Splitting the lentils: Clues to galaxy/black hole coevolution from the discovery of offset relations for non-dusty versus dusty (wet-merger-built) lenticular galaxies in the $M_{\mathrm{bh}}$-$M_{\ast ,\mathrm{spheroid}}$ diagram
• Molecular Gas in Candidate Double Barred Galaxies III. A Lack of Molecular Gas?
• Morphological and Kinematical Analysis of the Double-barred Galaxy NGC 3504 Using ALMA CO (2-1) Data
• Radio continuum of galaxies with H${}_2$O megamaser disks: 33 GHz VLA data