Scientific Results in Press

Shocked gas around CepA: evidence for multiple outflows from H₂S and SO₂ observations

C. Codella(¹), R. Bachiller(²), M. Benedettini(³) and P. Caselli(⁴)
(¹)Istituto di Radioastronomia, CNR, Sezione di Firenze, Largo E. Fermi 5, 50125 Firenze, Italy, (²)Observatorio Astronómico Nacional (IGN), Apartado 1143, E-28800, Alcalá de Henares (Madrid), Spain, (³)Istituto di Fisica dello Spazio Interplanetario, CNR, Area di Ricerca Tor Vergata, Via Fosso del Cavaliere 100, 00133 Roma, Italy, (⁴)INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

Abstract:
The Cepheus A star forming region has been investigated through a multiline H₂S and SO₂ survey at mm-wavelengths. Large scale maps and high-resolution line profiles reveal the occurrence of several outflows. CepA-East is associated with multiple mass loss processes: in particular, we detect a 0.6 pc jet-like structure which shows for the first time that the CepA-East YSOs are driving a collimated outflow moving towards the south. The observed outflows show different clumps associated with definitely different H₂S/SO₂ integrated emission ratios indicating that the gas chemistry in Cepheus A has been altered by the passage of shocks. H₂S appears to be more abundant than SO₂ in high velocity clumps, in agreement with chemical models. However, we also find quite narrow H₂S linewidths, suggesting of regions where the evaporated H₂S molecules had enough time to slow down but not to freeze out onto dust grains. Finally, the comparison between the line profiles indicates that the excitation conditions increase with the velocity, as expected for a propagation of collimated bow shocks.

MNRAS, in press

CO Emission from z>3 Radio Galaxies

C. De Breuck(¹), R. Neri(²) and A. Omont(¹)
(¹)Institute d'Astrophysique de Paris, 98bis Boulevard Arago, 75014 Paris, France, (²)Institute de Radio Astronomie Millimétrique, 38406 St. Martin d'Hères, France

Abstract:
We report on the detection of the CO(4-3) line with the IRAM Plateau de Bure Interferometer in two z>3 radio galaxies, doubling the number of successful detections in such objects. A comparison of the CO and Ly$\alpha$ velocity profiles indicates that in at least half of the cases, the CO is coincident in velocity with associated HI absorption seen against the Ly$\alpha$ emission. This strongly suggests that the CO and HI originate from the same gas reservoir, and could explain the observed redshift differences between the optical narrow emission lines and the CO. The CO emission traces a mass of H₂ 100-1000 times larger than the HI and HII mass traced by Ly$\alpha$, providing sufficient gas to supply the massive starbursts suggested by their strong thermal dust emission.

To appear in: Proceedings of the conference "Radio Galaxies: Past, present and future", Leiden, 11-15 Nov. 2002, eds. M. Jarvis et al., Elsevier Science