The extended HI halo of NGC 4945 as seen by MeerKAT

Abstract

Observations of the neutral atomic hydrogen (HI) in the nuclear starburst galaxy NGC 4945 with MeerKAT are presented. We find a large amount of halo gas, previously missed by HI observations, accounting for 6.8% of the total HI mass. This is most likely gas blown into the halo by star formation. Our maps go down to a $3\sigma$ column density level of $5\times 10^{18}c{m}^{-2}$ . We model the HI distribution using tilted-ring fitting techniques and find a warp on the galaxy's approaching and receding sides. The HI in the northern side of the galaxy appears to be suppressed. This may be the result of ionisation by the starburst activity in the galaxy, as suggested by a previous study. The origin of the warp is unclear but could be due to past interactions or ram pressure stripping. Broad, asymmetric HI absorption lines extending beyond the HI emission velocity channels are present towards the nuclear region of NGC 4945. Such broad lines suggest the existence of a nuclear ring moving at a high circular velocity. This is supported by the clear rotation patterns in the HI absorption velocity field. The asymmetry of the absorption spectra can be caused by outflows or inflows of gas in the nuclear region of NGC 4945. The continuum map shows small extensions on both sides of the galaxy's major axis that might be signs of outflows resulting from the starburst activity.

20 pages, 15 figures, 3 tables, accepted for publication in MNRAS

References in corpus (18)

• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• The cold gaseous halo of NGC 891
• SoFiA: a flexible source finder for 3D spectral line data
• Star formation sustained by gas accretion
• The Hubble flow around the CenA / M83 galaxy complex
• The HI absorption "Zoo"
• Evidence of a dynamically evolving Galactic warp
• The Global Star Formation Laws of Galaxies from a Radio Continuum Perspective
• HALOGAS: the properties of extraplanar HI in disc galaxies
• The Star Formation History of the Disk of the Starburst galaxy M82
• Super Star Clusters in the Central Starburst of NGC 4945
• 12CO 4-3 and [CI] 1-0 at the centers of NGC 4945 and Circinus
• Detection of 183 GHz water megamaser emission towards NGC 4945
• MeerKAT HI commissioning observations of MHONGOOSE galaxy ESO 302-G014
• A 5deg x 5deg deep HI survey of the M81 group
• MeerKAT-16 HI observation of the dIrr galaxy WLM
• Galaxies with Declining Rotation Curves
• Anomalous gas in ESO 149-G003: A MeerKAT-16 View

Cited by in corpus (4)

• Evidence for extended gaseous reservoirs around AGN at cosmic noon from ALMA CO(3-2) observations
• Evidence of extended [CII] and dust emission in local dwarf galaxies
• First resolved stellar halo kinematics of a MW-mass galaxy outside the Local Group: A flat counter-rotating halo in NGC 4945
• Gas accretion onto galaxies and Kelvin-Helmholtz turbulence