* Astronomy

Title: Cold and warm molecular gas in the outflow of 4C12.50
Authors: K. M. Dasyra, F. Combes

We present deep observations of the 12CO(1-0) and (3-2) lines in 4C12.50, carried out with the 30m telescope of the Institut de Radioastronomie Millimetrique. Our observations revealed the cold molecular gas component of a warm molecular gas outflow that was previously known from Spitzer Space Telescope data. The 12CO(3-2) profile indicates the presence of absorption at -950 km/s from systemic velocity with a central optical depth of 0.22. Its profile is similar to that of the HI absorption that was seen in radio data of this source. A potential detection of the (0-1) absorption enabled us to place an upper limit of 0.03 on its central optical depth, and to constrain the excitation temperature of the outflowing CO gas to >=65K assuming that the gas is thermalised. If the molecular clouds are fully obscuring their background millimetre continuum that is emitted by the radio core, the H2 column density is >=1.8*10^22 /cm². The outflow is then carrying an estimated cold H2 mass of at least 4.2*10³ solar masses along the nuclear line of sight. This mass will be even higher when integrated over several lines of sight, but if it were to exceed 3*10^9 solar masses, the outflow would most likely be seen in emission. Since the ambient cold gas reservoir of 4C12.50 is 1.0*10^10 solar masses, the outflowing-to-ambient mass ratio of the warm gas (37%) could be elevated with respect to that of the cold gas.

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