We report on the Herschel/PACS observations of OH in Mrk 231, with detections in 9 doublets observed within the PACS range, and present radiative transfer models for the outflowing OH. Signatures of outflowing gas are found in up to 6 OH doublets wit
h different excitation requirements. At least two outflowing components are identified, one with OH radiatively excited, and the other with low excitation, presumably spatially extended. Particularly prominent, the blue wing of the absorption detected in the in-ladder 2Pi_{3/2} J=9/2-7/2 OH doublet at 65 um, with E_lower=290 K, indicates that the excited outflowing gas is generated in a compact and warm (circum)nuclear region. Because the excited, outflowing OH gas in Mrk 231 is associated with the warm, far-IR continuum source, it is likely more compact (diameter of 200-300 pc) than that probed by CO and HCN. Nevertheless, its mass-outflow rate per unit of solid angle as inferred from OH is similar to that previously derived from CO, >~70x(2.5x10^{-6}/X_{OH}) Msun yr^{-1} sr^{-1}, where X_{OH} is the OH abundance relative to H nuclei. In spherical symmetry, this would correspond to >~850x(2.5x10^{-6}/X_{OH}) Msun yr^{-1}, though significant collimation is inferred from the line profiles. The momentum flux of the excited component attains ~15 L_{AGN}/c, with an OH column density of (1.5-3)x10^{17} cm^-2 and a mechanical luminosity of ~10^{11} Lsun. The detection of very excited OH peaking at central velocities indicates the presence of a nuclear reservoir of gas rich in OH, plausibly the 130-pc scale circumnuclear torus previously detected in OH megamaser emission, that may be feeding the outflow. An exceptional ^{18}OH enhancement, with OH/^{18}OH<~30 at both central and blueshifted velocities, is likely the result of interstellar-medium processing by recent starburst/SNe activity.
[Abridged] We present maps of the main cooling lines of the neutral atomic gas ([OI] at 63 and 145 micron and [CII] at 158 micron) and in the [OIII] 88 micron line of the starburst galaxy M82, carried out with the PACS spectrometer on board the Hersc
hel satellite. By applying PDR modeling we derive maps of the main ISM physical parameters, including the [CII] optical depth, at unprecedented spatial resolution (~300 pc). We can clearly kinematically separate the disk from the outflow in all lines. The [CII] and [OI] distributions are consistent with PDR emission both in the disk and in the outflow. Surprisingly, in the outflow, the atomic and the ionized gas traced by the [OIII] line both have a deprojected velocity of ~75 km/s, very similar to the average velocity of the outflowing cold molecular gas (~ 100 km/s) and several times smaller than the outflowing material detected in Halpha (~ 600 km/s). This suggests that the cold molecular and neutral atomic gas and the ionized gas traced by the [OIII] 88 micron line are dynamically coupled to each other but decoupled from the Halpha emitting gas. We propose a scenario where cold clouds from the disk are entrained into the outflow by the winds where they likely evaporate, surviving as small, fairly dense cloudlets (n_Hsim 500-1000 cm^-3, G_0sim 500- 1000, T_gassim300 K). We show that the UV photons provided by the starburst are sufficient to excite the PDR shells around the molecular cores. The mass of the neutral atomic gas in the outflow is gtrsim 5-12x 10^7 M_sun to be compared with that of the molecular gas (3.3 x 10^8 M_sun) and of the Halpha emitting gas (5.8 x 10^6 M_sun). The mass loading factor, (dM/dt)/SFR, of the molecular plus neutral atomic gas in the outflow is ~ 2. Energy and momentum driven outflow models can explain the data equally well, if all the outflowing gas components are taken into account.
We present Herschel-PACS observations of rest-frame mid-infrared and far-infrared spectral line emissions from two lensed, ultra-luminous infrared galaxies at high redshift: MIPS J142824.0+352619 (MIPS J1428), a starburst-dominated system at z = 1.3,
and IRAS F10214+4724 (F10214), a source at z = 2.3 hosting both star-formation and a luminous AGN. We have detected [OI]63 micron and [OIII]52 micron in MIPS J1428, and tentatively [OIII]52 micron in F10214. Together with the recent ZEUS-CSO [CII]158 micron detection in MIPS J1428 we can for the first time combine [OI], [CII] and far-IR (FIR) continuum measurements for photo-dissociation (PDR) modeling of an ultra-luminous (L_IR > 10^12 L_sun) star forming galaxy at the peak epoch of cosmic star formation. We find that MIPS J1428, contrary to average local ULIRGs, does not show a deficit in [OI] relative to FIR. The combination of far-UV flux G_0 and gas density n (derived from the PDR models), as well as the star formation efficiency (derived from CO and FIR) is similar to normal or starburst galaxies, despite the high infrared luminosity of this system. In contrast, F10214 has stringent upper limits on [OIV] and [SIII], and an [OIII]/FIR ratio at least an order of magnitude lower than local starbursts or AGN, similar to local ULIRGs.
We present self-consistent global, steady-state MHD models and synthetic optically thin synchrotron emission maps for the jet of M87. The model consist of two distinct zones: an inner relativistic outflow, which we identify with the observed jet, and
an outer cold disk-wind. While the former does not self-collimate efficiently due to its high effective inertia, the latter fulfills all the conditions for efficient collimation by the magneto-centrifugal mechanism. Given the right balance between the effective inertia of the inner flow and the collimation efficiency of the outer disk wind, the relativistic flow is magnetically confined into a well collimated beam and matches the measurements of the opening angle of M87 over several orders of magnitude in spatial extent. The synthetic synchrotron maps reproduce the morphological structure of the jet of M87, i.e. center-bright profiles near the core and limb-bright profiles away from the core. At the same time, they also show a local increase of brightness at some distance along the axis associated to a recollimation shock in the MHD model. Its location coincides with the position of the optical knot HST-1. In addition our best fitting model is consistent with a number of observational constraints such as the magnetic field in the knot HST-1, and the jet-to-counterjet brightness ratio.
We present new observations made with the IRAM 30m telescope of the J=1-0 and 3-2 lines of HCN and HCO^+ used to probe the dense molecular gas content in a sample of 17 local luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs). These obse
rvations have allowed us to derive an updated version of the power law describing the correlation between the FIR luminosity (L_FIR) and the HCN(1-0) luminosity (L_HCN(1-0)) of local and high-redshift galaxies. We present the first clear observational evidence that the star formation efficiency of the dense gas (SFE_dense), measured as the L_FIR/L_HCN(1-0) ratio, is significantly higher in LIRGs and ULIRGs than in normal galaxies, a result that has also been found recently in high-redshift galaxies. This may imply a statistically significant turn upward in the Kennicutt-Schmidt law derived for the dense gas at L_FIR >= 10^11 L_sun. We have used a one-phase Large Velocity Gradient (LVG) radiative transfer code to fit the three independent line ratios derived from our observations. The results of this analysis indicate that the [HCN]/[HCO^+] abundance ratios could be up to one order of magnitude higher than normal in a significant number of LIRGs and ULIRGs of our sample. An overabundance of HCN at high L_FIR implies that the reported trend in the L_FIR/L_HCN ratio as a function of L_FIR would be underestimating a potentially more dramatic change of the SFE_dense. Results obtained with two-phase LVG models corroborate that the L_HCN(1-0)-to-M_dense conversion factor must be lowered at high L_FIR. We discuss the implications of these findings for the use of HCN as a tracer of the dense molecular gas in local and high-redshift luminous infrared galaxies.
