Mass outflows driven by stars and active galactic nuclei are a key element in many current models of galaxy evolution. They may produce the observed black hole-galaxy mass relation and regulate and quench both star formation in the host galaxy and black hole accretion. However, observational evidence of such feedback processes through outflows of the bulk of the star forming molecular gas is still scarce. Here we report the detection of massive molecular outflows, traced by the hydroxyl molecule (OH), in far-infrared spectra of ULIRGs obtained with Herschel-PACS as part of the SHINING key project. In some of these objects the (terminal) outflow velocities exceed 1000 km/s, and their outflow rates (up to ∼1200 M ⊙ /yr) are several times larger than their star formation rates. We compare the outflow signatures in different types of ULIRGs and in starburst galaxies to address the issue of the energy source (AGN or starburst) of these outflows. We report preliminary evidence that ULIRGs with a higher AGN luminosity (and higher AGN contribution to L IR ) have higher terminal velocities and shorter gas depletion time scales. The outflows in the observed ULIRGs are able to expel the cold gas reservoirs from the centres of these objects within ∼10 6 -10 8 years.

We report the results from a systematic search for molecular (OH 119 µm) outflows with Herschel-PACS 1 in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7-µm silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than −50 km

We report initial results from the far-infrared fine structure line observations of a sample of 44 local starbursts, Seyfert galaxies and infrared luminous galaxies obtained with the PACS spectrometer on board Herschel. We show that the ratio between the far-infrared luminosity and the molecular gas mass, L FIR /M H2 , is a much better proxy for the relative brightness of the far-infrared lines than L FIR alone. Galaxies with high L FIR /M H2 ratios tend to have weaker fine structure lines relative to their far-infrared continuum than galaxies with L FIR /M H2 80 L ⊙ M ⊙ −1 . A deficit of the [C II] 158 µm line relative to L FIR was previously found with the ISO satellite, but now we show for the first time that this is a general aspect of all far-infrared fine structure lines, regardless of their origin in the ionized or neutral phase of the interstellar medium. The L FIR /M H2 value where these line deficits start to manifest is similar to the limit that separates between the two modes of star formation recently found in galaxies on the basis of studies of their gas-star formation relations. Our finding that the properties of the interstellar medium are also significantly different in these regimes provides independent support for the different star forming relations in normal disk galaxies and major merger systems. We use the spectral synthesis code Cloudy to model the emission of the lines. The expected increase of the ionization parameter with L FIR /M H2 can simultaneously explain the line deficits in the [C II], [N II] and [O I] lines.

In this paper, we use the very recent spectropolarimetric observations of β Cep collected by Henrichs et al. and propose for this star a consistent model of the large‐scale magnetic field and of the associated magnetically confined wind and circumstellar environment. A re‐examination of the fundamental parameters of β Cep in the light of the Hipparcos parallax indicates that this star is most likely a 12‐M⊙ star with a radius of 7 R⊙, effective temperature of 26 000 K and age of 12 Myr, viewed with an inclination of the rotation axis of about 60°. Using two different modelling strategies, we obtain that the magnetic field of β Cep can be approximately described as a dipole with a polar strength of , the axis of symmetry of which is tilted with respect to the rotation axis by about . Although one of the weakest detected to date, this magnetic field is strong enough to magnetically confine the wind of β Cep up to a distance of about 8 to 9 R∗. We find that both the X‐ray luminosity and variability of β Cep can be explained within the framework of the magnetically confined wind‐shock model of Babel & Montmerle, in which the stellar‐wind streams from both magnetic hemispheres collide with each other in the magnetic equatorial plane, producing a strong shock, an extended post‐shock region and a high‐density cooling disc. By studying the stability of the cooling disc, we obtain that field lines can support the increasing disc weight for no more than a month before they become significantly elongated in an effort to equilibrate the gravitational plus centrifugal force, thereby generating strong field gradients across the disc. The associated current sheet eventually tears, forcing the field to reconnect through resistive diffusion and the disc plasma to collapse towards the star. We propose that this collapse is the cause for the recurrent Be episodes of β Cep, and finally discuss the applicability of this model to He peculiar, classical Be and normal non‐supergiant B stars.