First Results with the ATCA 3mm Prototype System (10-Dec-2000)

Part 2: HCO⁺ absorption in the galaxy Centaurus A

The HCO⁺ spectra displayed below have been observed on December 10th, 2000, with the one baseline (CA03-CA04: 31m baseline, 1.5B array) 3mm prototype system of the Australia Telescope Compact Array.

• Original HCO⁺ absorption spectrum against the core of the nearby radio galaxy Centaurus A.
  The rest frequency of the HCO⁺ line is 89.188518 GHz. The spectrum is centred on 89.030 GHz which corresponds to the systemic velocity (approx. 550 km/s) of Cen A. The bandwidth is 32 MHz divided into 128 channels. The integration time was two hours. No calibration was applied.
• Here a preliminary gain and bandpass calibration of the above HCO⁺ absorption spectrum has been attempted. Please note that the velocity range covered in this narrow-band spectrum is smaller than the total known absorption range. Consequently, only the central absorption complex (537 - 560 km/s) is seen in detail. This spectrum is Hanning smoothed.
• Further low and high resolution ATCA observations of Cen A will follow soon (winter 2001). The largest bandwidth (about 180 MHz, divided into 90 channels ) will be used to study the overall spectrum, followed by more detailed spectra. First imaging might be attempted with an ATCA three baseline prototype system.

See also

• A Supermassive Black Hole in a Nearby Galaxy: ISAAC Inspects the Center of Centaurus A
• Wiklind & Combes 1997