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.

We report the detection of far-IR CO rotational emission from the prototypical Seyfert 2 galaxy NGC 1068. Using Herschel-PACS, we have detected 11 transitions in the J upper = 14 − 30 (E upper /k B = 580 − 2565 K) range, all of which are consistent with arising from within the central 10 ′′ (700 pc). The detected transitions are modeled as arising from 2 different components: a moderate excitation (ME) component close to the galaxy systemic velocity, and a high excitation (HE) component that is blueshifted by ∼80 km s −1 . We employ a large velocity gradient (LVG) model and derive n H2 ∼ 10 5.6 cm −3 , T kin ∼ 170 K, and M H 2 ∼ 10 6.7 M ⊙ for the ME component, and n H2 ∼ 10 6.4 cm −3 , T kin ∼ 570 K, and M H 2 ∼ 10 5.6 M ⊙ for the HE component, although for both components the uncertainties in the density and mass are ±(0.6 − 0.9) dex. Both components arise from denser and possibly warmer gas than traced by low-J CO transitions, and the ME component likely makes a significant contribution to the mass budget in the nuclear region. We compare the CO line profiles with those of other molecular tracers observed at higher spatial and spectral resolution, and find that the ME transitions are consistent with these lines arising in the ∼200 pc diameter ring of material traced by H 2 1-0 S(1) observations. The blueshift of the HE lines may also be consistent with the bluest regions of this H 2 ring, but a better kinematic match is found with a clump of infalling gas ∼40 pc north of the AGN. We consider potential heating mechanisms, and conclude that X-ray or shock heating of both components is viable, while far-UV heating is unlikely. We discuss the prospects of placing the HE component near the AGN, and conclude that while the moderate thermal pressure precludes an association with the ∼1 pc radius H 2 O maser disk, the HE component could potentially be located only a few parsecs more distant from the AGN, and might then provide the N H ∼ 10 25 cm −2 column obscuring the nuclear hard X-rays. Finally, we also report sensitive upper limits extending up to J upper = 50, which place constraints on a previous model prediction for the CO emission from the X-ray obscuring torus.

Using 100-fs optical laser pulses, we have been able to excite and probe spin dynamics in the rare-earth orthoferrite ErFeO 3 . The investigation was performed in a broad temperature range with the focus on the vicinities of the compensation point T comp ≈ 47 K and the spin reorientation transition region in the interval 86 K T 99 K. Spin precession excited by the laser pulse was present in a large part of the investigated temperature range, but was especially strong near the spin reorientation region. In this region the laser pulse also caused an ultrafast spin reorientation. By changing the laser pulse fluence, we could vary both the reorientation amplitude and the reorientation speed. We show that the laser-induced spin dynamics in ErFeO 3 is caused in part by heating and in part by the inverse Faraday effect. Comparing to the results of similar experiments in other rare-earth orthoferrites, we found the speed of the laser-induced spin reorientation to be significantly lower. We attribute this finding to the weaker electron-phonon coupling of the Er 3+ 4f electrons with the lattice.

Abstract. We present the results of an extensive observing campaign on the O7.5 III star ξ Persei. The UV observations were obtained with the International Ultraviolet Explorer. ξ Per was monitored continuously in October 1994 during 10 days at ultraviolet and visual wavelengths. The ground-based optical observations include magnetic field measurements, Hα and He i λ6678 spectra, and were partially covered by photometry and polarimetry. We describe a method to automatically remove the variable contamination of telluric lines in the groundbased spectra. The aim of this campaign was to search for the origin of the cyclical wind variability in this star. We determined a very accurate period of 2.086(2) d in the resonance lines of Si iv and in the subordinate N iv and Hα line profiles. The epochs of maximum absorption in the UV resonance lines due to discrete absorption components (DACs) coincide in phase with the maxima in blue-shifted Hα absorption. This implies that the periodic variability originates close to the stellar surface. The phase−velocity relation shows a maximum at −1400 km s −1 . The general trend of these observations can be well explained by the corotating interaction region (CIR) model. In this model the wind is perturbed by one or more fixed patches on the stellar surface, which are most probably due to small magnetic field structures. Our magnetic field measurements gave, however, only a null-detection with a 1σ errorbar of 70 G in the longitudinal component. Some observations are more difficult to fit into this picture. The 2-day period is not detected in the photospheric/transition region line He i λ6678. The dynamic spectrum of this line shows a pattern indicating the presence of non-radial pulsation, consistent with the previously reported period of 3.5 h. The edge variability around −2300 km s −1 in the saturated wind lines of C iv and N v is nearly identical to the edge variability in the unsaturated Si iv line, supporting the view that this type of variability is also due to the moving DACs. A detailed analysis using Fourier reconstructions reveals that each DAC actually consists of 2 different components: a "fast" and a "slow" one which merge at higher velocities.

Time-resolved magneto-optical imaging of laser-excited rare-earth orthoferrite ðSmPrÞFeO 3 demonstrates that a single 60 fs circularly polarized laser pulse is capable of creating a magnetic domain on a picosecond time scale with a magnetization direction determined by the helicity of light. Depending on the light intensity and sample temperature, pulses of the same helicity can create domains with opposite magnetizations. We argue that this phenomenon relies on a twofold effect of light which (i) instantaneously excites coherent low-amplitude spin precession and (ii) triggers a spin reorientation phase transition. The former dynamically breaks the equivalence between two otherwise degenerate states with opposite magnetizations in the high-temperature phase and thus controls the route of the phase transition.