Molecular tendrils feeding star formation in the Eye of the Medusa - The Medusa merger in high resolution 12CO 2-1 maps

摘要

Studying molecular gas properties in merging galaxies gives us importantclues to the onset and evolution of interaction-triggered starbursts. NGC4194is particularly interesting to study since its FIR-to-CO luminosity ratiorivals that of ULIRGs,despite its lower luminosity compared to ULIRGs, whichindicates a high star formation efficiency that is relative to even mostspirals and ULIRGs.We study the molecular medium at an angular resolution of0.65"x .52" through our observations of CO2-1 emission using the SMA. Wecompare our CO2-1 maps with optical HST and high angular resolution radiocontinuum images to study the relationship between molecular gas and othercomponents of the starburst region. The molecular gas is tracing thecomplicated dust lane structure of NGC4194 with the brightest emission beinglocated in an off-nuclear ring-like structure with ~320pc radius, the Eye ofthe Medusa. The bulk CO emission of the ring is found south of the kinematicalcenter of NGC4194. The northern tip of the ring is associated with the galaxynucleus, where the radio continuum has its peak. A prominent, secondaryemission maximum in the radio continuum is located inside the molecular ring.This suggests that the morphology of the ring is partially influenced bymassive supernova explosions. From the combined evidence, we propose that theEye of the Medusa contains a shell of swept up material where we identify anumber of giant molecular associations. We propose that the Eye may be the siteof an efficient starburst of 5-7M_sun/yr, but it would still constitute only afraction of the 30-50M_sun/yr SFR of NGC4194. Furthermore, we find that ~50% ofthe molecular mass of NGC4194 is found in extended filamentary-like structurestracing the minor and major axis dust lanes. We suggest that molecular gas istransported along these lanes providing the central starburst region with fuel.