Sub-arcsecond imaging of the radio continuum and neutral hydrogen in the Medusa merger

Abstract

We present sub-arcsecond, Multi-Element Radio Linked Interferometer (MERLIN) observations of the decimetre radio continuum structure and neutral hydrogen (HI) absorption from the nuclear region of the starburst galaxy NGC 4194 (the Medusa Merger). The continuum structure of the central kiloparsec of the Medusa has been imaged, revealing a pair of compact radio components surrounded by more diffuse, weak radio emission. Using the constraints provided by these observations and those within the literature we conclude that the majority of this radio emission is related to the ongoing star-formation in this merger system. With these observations we also trace deep HI absorption across the detected radio continuum structure. The absorbing HI gas structure exhibits large variations in column densities. The largest column densities are found toward the south of the nuclear radio continuum, co-spatial with both a nuclear dust lane and peaks in ${}^{12}$CO (1->0) emission. The dynamics of the HI absorption, which are consistent with lower resolution ${}^{12}$CO emission observations, trace a shallow north-south velocity gradient of ~320km/s/kpc. This gradient is interpreted as part of a rotating gas structure within the nuclear region. The HI and CO velocity structure, in conjunction with the observed gas column densities and distribution, is further discussed in the context of the fuelling and gas physics of the ongoing starburst within the centre of this merger.

12 pages, 5 figures, to appear in A&A

References in corpus (2)

• Parsec-Scale Radio Structure of the Double Active Nucleus of NGC 6240
• High resolution imaging of the radio continuum and neutral gas in the inner kiloparsec of the radio galaxy 3C293

Cited by in corpus (5)

• The NGC 1614 Interacting Galaxy: Molecular Gas Feeding a "Ring of Fire"
• Major impact from a minor merger - The extraordinary hot molecular gas flow in the Eye of the NGC 4194 Medusa galaxy
• Molecular tendrils feeding star formation in the Eye of the Medusa - The Medusa merger in high resolution 12CO 2-1 maps
• Stars and gas in the Medusa merger
• Ionized Gas Kinematics at High Resolution IV: Star Formation and a Rotating Core in the Medusa (NGC 4194)