Spatial distribution and kinematics of the molecular material associated with $\eta$ Carinae

Abstract

Single-dish sub-millimeter observations have recently revealed the existence of a substantial, chemically peculiar, molecular gas component located in the innermost circumstellar environment of the very massive luminous blue variable star $\eta$ Carinae. Here, we present 5$"$-resolution interferometric observations of the 1$\to$0 rotational transition of hydrogen cyanide (HCN) obtained with the Australia Telescope Compact Array (ATCA) toward this star. The emission is concentrated in the central few arcseconds around $\eta$ Carinae and shows a clear 150 km s${}^{-1}$ velocity gradient running from west-north-west (blue) to east-south-east (red). Given the extent, location, and kinematics of this molecular material, we associate it with the complex of dusty arcs and knots seen in mid-infrared emission near the center of the Homunculus nebula. Indeed, the shielding provided by this dust could help explain how molecules survive in the presence of the intense UV radiation field produced by $\eta$ Carinae. The dust located in the central few arcseconds around $\eta$ Carinae and the molecular component described here have most likely formed in situ, out of material expelled by the massive interacting binary system. Thus, $\eta$ Carinae offers us a rare glimpse on the processes leading to the formation of dust and molecules around massive stars that are so relevant to the interpretation of dust and molecule detections at high redshifts.

Accepted in ApJ

References in corpus (3)

• He II $\lambda$4686 emission from the massive binary system in $\eta$ Car: constraints to the orbital elements and the nature of the periodic minima
• Light Echoes from Eta Carinae's Great Eruption: Spectrophotometric Evolution and the Rapid Formation of Nitrogen-rich Molecules
• $\eta$ Carinae Baby Homunculus Uncovered by ALMA

Cited by in corpus (9)

• $\eta$ Carinae's Dusty Homunculus Nebula from Near-Infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity
• A disrupted molecular torus around Eta Carinae as seen in 12CO with ALMA
• A moderately precise dynamical age for the Homunculus of Eta Carinae based on 13 years of HST imaging
• Eta Carinae & the Homunculus: Far Infrared, Sub-millimeter Spectral Lines
• The peculiar chemistry of the inner ejecta of Eta Carina
• CO, Water, and Possible Methanol in Eta Carinae Approaching Periastron
• First detection of silicon-bearing molecules in $\eta$ Car
• A warm molecular ring in AG Car: composing the mass-loss puzzle
• NIKA2 observations around LBV stars: emission from stars and circumstellar material