We report on our observations of the 79 and 119 µm doublet transitions of OH for 24 local (z<0.262) ULIRGs observed with Herschel-PACS as part of the Herschel ULIRG Survey (HERUS). Some OH119 profiles display a clear P-Cygni shape and therefore imply outflowing OH gas, other profiles are predominantly in absorption or are completely in emission. We find that the relative strength of the OH emission component decreases as the silicate absorption increases. This locates the OH outflows inside the obscured nuclei. The maximum outflow velocities for our sources range from less than 100 to ∼2000 km s −1 , with 15/24 (10/24) sources showing OH absorption at velocities exceeding 700 km s −1 (1000 km s −1 ). Three sources show maximum OH outflow velocities exceeding that of Mrk231. Since outflow velocities above 500-700 km s −1 are thought to require an active galactic nucleus (AGN) to drive them, about 2/3 of our ULIRG sample may host AGN-driven molecular outflows. This finding is supported by the correlation we find between the maximum OH outflow velocity and the IR-derived bolometric AGN luminosity. No such correlation is found with the IR-derived star formation rate. The highest outflow velocities are found among sources which are still deeply embedded. We speculate that the molecular outflows in these sources may be in an early phase of disrupting the nuclear dust veil before these sources evolve into less obscured AGN. Four of our sources show high-velocity wings in their [C II] fine-structure line profiles implying neutral gas outflow masses of at least 2-4.5×10 8 M ⊙ .

We present optical spectroscopy obtained with the Space Telescope Imaging Spectrograph of five young massive star clusters in the starburst galaxy M82. A detailed analysis is performed for one cluster ‘M82‐A1’ and its immediate environment in the starburst core. From Hubble Space Telescope archive images, we find that it is elliptical with an effective radius of 3.0 ± 0.5 pc and is surrounded by a compact (r= 4.5 ± 0.5 pc) H ii region. We determine the age and reddening of M82‐A1 using synthetic spectra from population synthesis models by fitting both the continuum energy distribution and the depth of the Balmer jump. We find an age of 6.4 ± 0.5 Myr and a photometric mass estimate of M= 7–13 × 105 M⊙. We associate its formation with the most recent starburst event 4–6 Myr ago. We find that the oxygen abundance of the H ii region surrounding M82‐A1 is solar or slightly higher. The H ii region has a high pressure P/k= 1–2 × 107 cm−3 K. The diffuse gas in region A has a slightly lower pressure, which together with the broad Hα emission‐line width, suggests that both the thermal and turbulent pressures in the M82 starburst core are unusually high. We discuss how this environment has affected the evolution of the cluster wind for M82‐A1. We find that the high pressure may have caused the pressure‐driven bubble to stall. We also obtain spectroscopic ages for clusters B1‐2 and B2‐1 in the ‘fossil’ starburst region and for the intermediate age clusters F and L. These are consistent with earlier studies and demonstrate that star formation activity, sufficiently intense to produce super star clusters, has been going on in M82 during the past Gyr, perhaps in discrete and localized episodes.

We present optical integral field unit (IFU) observations (VLT/VIMOS-IFU and WIYN/SparsePak), and associated archival deep Hα imaging (MPG/ESO 2.2 m WFI), of the nearby starburst galaxy NGC 253. With VIMOS we observed the nuclear region and southern superwind outflow in detail with five pointings, and with the WIYN/SparsePak IFU we observed two partially overlapping regions covering the central disc and northern halo. The high signal-to-noise ratio of the data and spectral resolution (80-90 km s −1 ) enable us to accurately decompose the emission line profiles into multiple components.The combination of these data sets, together with the wealth of information on NGC 253 available in the literature, allows us to study the starburst-driven superwind in great detail. We investigate the known minor axis outflow cone, which is well-defined in the Hα imaging and kinematics between radii of 280 and 660 pc from the nucleus. Kinematic modelling indicates a wide opening angle (∼60 • ), an inclination consistent with that of the disc and deprojected outflow speeds of a few 100 km s −1 that increase with distance above the plane. The [N II]/Hα and [S II]/Hα line ratio maps imply that a significant fraction of the wind optical emission lines arise from shocked gas, with localized pockets/filaments of strongly shocked gas. From the kinematics, the cone appears partially closed in at least one place, and very broad Hα linewidths (>400 km s −1 full width at half maximum) suggest there is material filling the cone in some regions. Extrapolation of the cone to its apex shows it is not centred on the starburst nucleus, suggesting the wind is deflected and collimated by the dense circumnuclear material. We discuss the implications of these findings on our understanding of the origins and evolution of the superwind. No evidence for an outflow is found on the north-western side of the disc out to >2 kpc in our optical data, due to obscuration by the foreground disc. The lack of an obvious connection between the inner (r < 1 kpc) Hα and X-ray bright outflow cone and the large-scale (r 10 kpc) X-ray 'horns' is also discussed.

A study of the blue compact dwarf (BCD) galaxy Mrk 996 based on high‐resolution optical Very Large Telescope Visible Multi‐Object Spectrograph integral field unit spectroscopy is presented. Mrk 996 displays multicomponent line emission, with most line profiles consisting of a narrow, central Gaussian [full width at half‐maximum (FWHM) ∼ 110 km s−1] with an underlying broad component (FWHM ∼ 400 km s−1). The broad H i Balmer component splits into two separate broad components inside a 1.5‐arcsec radius from the nucleus; these are attributed to a two‐armed minispiral. This spiral‐like nucleus rotates in the same sense as the extended narrow line ionized gas but is offset by ∼50 km s−1 from the systemic velocity of the galaxy. The rotation curve of Mrk 996 derived from the Hα narrow component yields a total mass of 5 × 108 M⊙ within a radius of 3 kpc. From the Hα luminosity we infer a global star formation rate of ∼2 M⊙ yr−1. The high excitation energy, high critical density [O iii]λ4363 and [N ii]λ5755 lines are only detected from the inner region and exist purely in broad component form, implying unusual excitation conditions. Surface brightness, radial velocity and FWHM maps for several emission components are presented. A separate physical analysis of the broad and narrow emission line regions is undertaken. We derive an upper limit of 10 000 K for the electron temperature of the narrow line gas, together with an electron density of 170 cm−3, typical of normal H ii regions. For the broad line component, measured [O iii] and [Fe iii] diagnostic line ratios are consistent with a temperature of 11 000 K and an electron density of 107 cm−3. The broad line emission regions show N/H and N/O enrichment factors of ∼20 relative to the narrow line regions, but no He/H, O/H, S/H or Ar/H enrichment is inferred. Previous studies indicated that Mrk 996 showed anomalously high N/O ratios compared with BCDs of a similar metallicity. Our multicomponent analysis yields a revised metallicity of ≥0.5 Z⊙ (12 + log O/H = 8.37) for both the narrow and broad gas components, significantly higher than previous studies. As a result the narrow line region's N/O ratio is now typical for the galaxy's metallicity. The narrow line component's N/O ratio peaks outside the core region, spatially correlating with ∼3‐Myr‐old stellar populations. The dominant line excitation mechanism is photoionization by the ∼3000 Wolf–Rayet stars and ∼150 000 O‐type stars estimated to be present in the core. This is indeed a peculiar BCD, with extremely dense zones of gas in the core, through which stellar outflows and possible shock fronts permeate contributing to the excitation of the broad line emission.

We present Very Large Telescope (VLT)/VIsible MultiObject Spectrograph integral field unit (VIMOS‐IFU) emission‐line spectroscopy of a volume‐limited sample of 18 southern ultraluminous infrared galaxies (ULIRGs) selected with z < 0.09 and δ < 10. By covering a wide range of ULIRG types, including many systems that have received very little previous attention, this data set provides an important set of templates for comparison with high‐redshift galaxies. We employed an automated Gaussian line‐fitting programme to decompose the emission‐line profiles of Hα, [N ii], [S ii] and [O i] into individual components, and chart the Hα kinematics, and the ionized gas excitations and densities. 11 out of 18 of our galaxies show evidence for outflowing warm ionized gas with speeds between 500 and a few 1000 km s−1, with the fastest outflows associated with systems that contain an active galactic nucleus. Our spatially resolved spectroscopy has allowed us to map the outflows, and in some cases determine for the first time to which nucleus the wind is associated. In three of our targets we find line components with widths >2000 km s−1 over spatially extended regions in both the recombination and forbidden lines; in two of these three, they are associated with a known Sy2 nucleus. Eight galaxies have clear rotating gaseous discs, and for these we measure rotation velocities, virial masses, and calculate Toomre Q parameters. We find radial gradients in the emission‐line ratios in a significant number of systems in our study. We attribute these gradients to changes in ionizing radiation field strength, most likely due to an increasing contribution of shocks with radius. We conclude with a detailed discussion of the results for each individual system, with reference to the existing literature. Our observations demonstrate that the complexity of the kinematics and gas properties in ULIRGs can only be disentangled with high sensitivity, spatially resolved IFU observations. Many of our targets are ideal candidates for future high spatial resolution follow‐up observations.