Ionized gas in the starburst core and halo of NGC 1140

Abstract

We present deep WIYN H_alpha SparsePak and DensePak spatially-resolved optical spectroscopy of the dwarf irregular starburst galaxy NGC 1140. The different spatial resolutions and coverage of the two sets of observations have allowed us to investigate the properties and kinematics of the warm ionized gas within both the central regions of the galaxy and the inner halo. We find that the position angle of the H_alpha rotation axis for the main body of the galaxy is consistent with the HI rotation axis at PA = 39 deg, but that the ionized gas in the central 20x20 arcsecs (~2x2 kpc) is kinematically decoupled from the rest of the system, and rotates at a PA approximately perpendicular to that of the main body of the galaxy at +40 deg. We find no evidence of coherent large-scale galactic outflows. Instead multiple narrow emission line components seen within a radius of ~1-1.5 kpc, and high [SII]/H_alpha ratios found beyond ~2 kpc implying a strong contribution from shocks, suggest that the intense star formation is driving material outwards from the main star forming zone in the form of a series of interacting superbubbles/shells. A broad component (100<FWHM<230 km/s) to the H_alpha line is identified throughout galaxy disk out to >2 kpc. Based on recent work, we conclude that it is produced in turbulent mixing layers on the surfaces of cool gas knots embedded within the ISM, set up by the feedback from young massive star clusters. Our data suggest a physical limit to the radius where the broad emission line component is significant, and we propose that this limit marks a significant transition point in the development of the galactic outflow, where turbulent motion becomes less dominant. This mirrors what has recently been found in another similar irregular starburst galaxy NGC 1569.

13 pages, 9 figures (6 colour). Accepted for publication in MNRAS

References in corpus (7)

• Gemini GMOS/IFU spectroscopy of NGC 1569 - I: Mapping the properties of a young star cluster and its environment
• The Optical Structure of the Starburst Galaxy M82. II. Nebular Properties of the Disk and Inner-Wind
• Studying the galactic outflow in NGC 1569
• Gemini GMOS/IFU spectroscopy of NGC 1569 - II: Mapping the roots of the galactic outflow
• The Massive Star Population in the Giant HII Region Tol89 in NGC5398
• The broad H-alpha, [O III] line wings in stellar supercluster A of NGC2363 and the turbulent mixing layer hypothesis
• Cluster and nebular properties of the central star-forming region of NGC 1140

Cited by in corpus (6)

• Molecular depletion times and the CO-to-H2 conversion factor in metal-poor galaxies
• The ionized gas in the central region of NGC 5253: 2D mapping of the physical and chemical properties
• A kinematic study of the neutral and ionised gas in the irregular dwarf galaxies IC 4662 and NGC 5408
• Star formation driven galactic winds in UGC 10043
• Integral field observations of the blue compact galaxy Haro14. Star formation and feedback in dwarf galaxies
• Characterizing the outer disk of eXtended-UV galaxies in the optical domain with deep surveys