We report the detection of a massive neutral gas outflow in the z = 2.09 gravitationally lensed dusty star-forming galaxy HATLAS J085358.9+015537 (G09v1.40), seen in absorption with the OH+(11-10) transition using spatially resolved (0"5 × 0"4) Atacama Large Millimeter/submillimeter Array (ALMA) observations. The blueshifted OH+ line is observed simultaneously with the CO(9-8) emission line and underlying dust continuum. These data are complemented by high-angular-resolution (0"17 × 0"13) ALMA observations of CH+(1-0) and underlying dust continuum, and Keck 2.2 μm imaging tracing the stellar emission. The neutral outflow, dust, dense molecular gas, and stars all show spatial offsets from each other. The total atomic gas mass of the observed outflow is 6.7 × 109M⊙, >25% as massive as the gas mass of the galaxy. We find that a conical outflow geometry best describes the OH+ kinematics and morphology and derive deprojected outflow properties as functions of possible inclination (0°.38-64°). The neutral gas mass outflow rate is between 83 and 25,400 M⊙ yr-1, exceeding the star formation rate (788 ± 300M⊙ yr-1) if the inclination is >3°.6 (mass-loading factor = 0.3-4.7). Kinetic energy and momentum fluxes span (4.4-290) × 109 L⊙ and (0.1-3.7) × 1037 dyne, respectively (energy-loading factor = 0.013-16), indicating that the feedback mechanisms required to drive the outflow depend on the inclination assumed. We derive a gas depletion time between 29 and 1 Myr, but find that the neutral outflow is likely to remain bound to the galaxy unless the inclination is small and may be reaccreted if additional feedback processes do not occur.

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Our observations include photometric and spectral-line observations from both the PACS and SPIRE instruments onboard Herschel, obtained as part of the large KINGFISH (Key Insights on Nearby Galaxies: a Far- Infrared Survey with Herschel, Kennicutt+ 2011PASP..123.1347K) and BtP (Beyond the Peak; OT1_jsmith1; P.I. J.D. Smith) projects. [NII]205um BtP observations were performed with SPIRE-FTS intermediate mapping, which is a 4-point dither. E. Pellegrini et al. (2017, in preparation) will contain a full description of the observations and reductions. [CII]158um and [NII]122um emission lines, and 70 and 160um continuum maps have been observed as part the Herschel Open Time Key Program KINGFISH. The data and the associated reduction are described in Kennicutt+ (2011PASP..123.1347K) and Croxall+ (2013ApJ...777...96C). (2 data files).@en

The [C ii] 158 μm fine-structure line is the brightest emission line observed in local star-forming galaxies. As a major coolant of the gas-phase interstellar medium, [C ii] balances the heating, including that due to far-ultraviolet photons, which heat the gas via the photoelectric effect. However, the origin of [C ii] emission remains unclear because C⁺ can be found in multiple phases of the interstellar medium. Here we measure the fractions of [C ii] emission originating in the ionized and neutral gas phases of a sample of nearby galaxies. We use the [N ii] 205 μm fine-structure line to trace the ionized medium, thereby eliminating the strong density dependence that exists in the ratio of [C ii]/[N ii] 122 μm. Using the FIR [C ii] and [N ii] emission detected by the KINGFISH (Key Insights on Nearby Galaxies: a Far- Infrared Survey with Herschel) and Beyond the Peak Herschel programs, we show that 60%-80% of [C ii] emission originates from neutral gas. We find that the fraction of [C ii] originating in the neutral medium has a weak dependence on dust temperature and the surface density of star formation, and has a stronger dependence on the gas-phase metallicity. In metal-rich environments, the relatively cooler ionized gas makes substantially larger contributions to total [C ii] emission than at low abundance, contrary to prior expectations. Approximate calibrations of this metallicity trend are provided.

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The [NII] 122 and 205 um transitions are powerful tracers of the ionized gas in the ISM: (1) the [NII] 122/205 line ratio can be used to measure the electron density of the low-excitation, ionized gas, and (2) the intensity of these lines is directly related to the flux of ionizing photons, probing the most recent star formation activity. The study of these applications in nearby galaxies is specially relevant now that ALMA can observe both [NII] transitions at z>2. In this talk I will present Herschel observations of these pair of [NII] far-infrared lines in 21 nearby galaxies selected from the KINGFISH and Beyond the Peak samples. I will discuss the reliability of the [NII] lines as star formation tracers, and how the electron density of the ionized gas is related to other relevant ISM properties (e.g., radiation field strength, star formation activity, dust temperature, etc). @en