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Register a new userQuantifying the AGN-driven outflows in ULIRGs (QUADROS) IV: HST/STIS spectroscopy of the sub-kpc warm outflow in F14394+5332
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Considerable uncertainties remain about the nature of warm, AGN-driven outflows and their impact on the evolution of galaxies. This is because the outflows are often unresolved in ground-based observations. As part of a project to study the AGN outflows in some of the most rapidly evolving galaxies in the local Universe, here we present HST/STIS observations of F14394+5332E that resolve the sub-kpc warm outflow for the first time in a ULIRG. The observations reveal a compact, high-ionization outflow region (r_max~0.9 kpc) set in a more extensive (r_max~1.4 kpc) halo that is kinematically quiescent and has a lower ionization state. A large line width (600 < FWHM < 1500 km/s) is measured throughout the outflow region, and the outflowing gas shows a steep velocity gradient with radius, with the magnitude of the blueshifted velocities increasing from ~500 to 1800 km/s from the inner to the outer part of the outflow. We interpret the observations in terms of the local acceleration, and hydrodynamic destruction, of dense clouds as they are swept up in a hot, low density wind driven by the AGN. We discuss the implications for measuring the mass outflow rates and kinetic powers for the AGN-driven outflows in such objects.
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The true importance of the warm, AGN-driven outflows for the evolution of galaxies remains uncertain. Measurements of the radial extents of the outflows are key for quantifying their masses and kinetic powers, and also establishing whether the AGN outflows are galaxy-wide. Therefore, as part of a larger project to investigate the significance of warm, AGN-driven outflows in the most rapidly evolving galaxies in the local universe, here we present deep Hubble Space Telescope ( HST) narrow-band [OIII]$lambda$5007 observations of a complete sample of 8 nearby ULIRGs with optical AGN nuclei. Combined with the complementary information provided by our ground-based spectroscopy, the HST images show that the warm gas outflows are relatively compact for most of the objects in the sample: in three objects the outflow regions are barely resolved at the resolution of HST ($0.065 < R_{[OIII]} < 0.12$ kpc); in a further four cases the outflows are spatially resolved but with flux weighted mean radii in the range $0.65 < R_{[OIII]} < 1.2$ kpc; and in only one object (Mrk273) is there clear evidence for a more extended outflow, with a maximum extent of $R_{[OIII]}sim5$ kpc. Overall, our observations show little evidence for the galaxy-wide outflows predicted by some models of AGN feedback.
We present an optical spectroscopic study of a 90% complete sample of 17 nearby ULIRGs with optical Seyfert nuclei, with the aim of investigating the nature of the nuclear warm gas outflows. A high proportion (94%) of our sample show disturbed emission line kinematics in the form of broad (FWHM > 500 km s-1) and/or strongly blueshifted (Delta V < -150 km s-1) emission line components. This proportion is significantly higher than found in a comparison sample of non-Sy ULIRGs (19%). We also find evidence that the [OII]5007,4959 emission lines in Sy-ULIRGs are broader and more asymmetric that in samples of non-ULIRG Seyferts. The Sy-ULIRG sample encompasses a wide diversity of emission line profiles. In most individual objects we are able to fit the profiles of all the emission lines with a kinematic model derived from the strong [OIII]4959,5007 lines, using between 2 and 5 Gaussian components. From these fits we derive diagnostic line ratios that are used to investigate the ionization mechanisms for the different kinematic components. We show that, in general, the line ratios are consistent with gas of super-solar abundance photoionized by a combination of AGN and starburst activity, with an increasing contribution from the AGN with increasing FWHM of the individual kinematic components, and the AGN contribution dominating for the broadest components. However, shock ionization cannot be ruled out in some cases. Our derived upper limits on the mass outflows rates and kinetic powers of the emission line outflows show that they can be as energetically significant as the neutral and molecular outflows in ULIRGs-consistent with the requirements of the hydrodynamic simulations that include AGN feedback. However, the uncertainties are large, and more accurate estimates of the radii, densities and reddening of the outflows are required to put these results on a firmer footing.
Warm absorber (WA) is an ionised gas present in the line of sight to the AGN central engine. The effect of the absorber is imprinted in the absorption lines observed in X-ray spectra of AGN. In this work, we model the WA in Seyfert 1 galaxy Mrk 509 using its recently published shape of broad band spectral energy distribution (SED) as a continuum illuminating the absorber. Using the photoionization code {sc Titan}, recently we have shown that the absorption measure distribution (AMD) found for this object can be successfully modelled as a single slab of gas in total pressure (radiation+gas) equilibrium, contrary to the usual models of constant density multiple slabs. We discuss the transmitted spectrum that would be recorded by an observer after the radiation from the nucleus passes through the WA.
We analyze high-resolution (400pc) 220GHz continuum and CO(2-1) ALMA observations of a representative sample of 23 local (z<0.165) ULIRG systems (34 individual nuclei) as part of the Physics of ULIRGs with MUSE and ALMA (PUMA) project. The deconvolved half-light radii of the 220GHz continuum sources are between <60-350 pc (median 90pc). We associate these regions with the regions emitting the bulk of the infrared luminosity. The good agreement, within a factor of 2, between the 220GHz fluxes and the extrapolation of the infrared gray-body, and the small synchrotron and free-free contributions support this assumption. The cold molecular gas emission sizes, r_CO, are 60-700 pc and are similar in advanced mergers and early interacting systems. On average, r_CO are 2.5 times larger than the continuum. We derive L_IR and cold molecular gas surface densities: log Sigma(L_IR)=11.5-14.3 Lsun/kpc^2 and log Sigma(H2)=2.9-4.2 Msun/pc^2. Assuming that the L_IR is produced by star-formation, this corresponds to median Sigma(SFR)=2500 Msun/yr/kpc^2 which would imply extremely short depletion times, <1-15 Myr, and unphysical SF efficiencies >1 for 70% of the sample. Therefore, this favors the presence of obscured AGN that could dominate the L_IR. We also classify the ULIRG nuclei in two groups: (a) compact nuclei (r<130 pc) with high mid-IR excess emission found in optically classified AGN; and (b) nuclei following a relation with decreasing mid-IR excess for decreasing r. 60% of the interacting nuclei lie in the low end (<130 pc) of this relation, while only 30% of the advanced mergers do so, suggesting that in the early interaction phases the activity occurs in more compact and obscured regions. About two thirds of the nuclei are above the Eddington limit which is consistent with the detection of massive outflows in local ULIRGs and the potential role of radiation pressure in the launching process.
We have carried out a spatio-kinematic study of the outflow from the classical T Tauri star DG Tau using the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). A series of seven spatially offset long-slit spectra spaced by 0.07 were obtained along the axis of the outflow to build up a 3-D intensity-velocity ``cube in various forbidden emission lines (FELs) and Ha. Here we present high spatial resolution synthetic line images close to the star in distinct radial velocity intervals (from ~ +50 km/s to ~ -450 km/s in four bins, each ~ 125 km/s wide). The lowest velocity emission is also examined in finer detail (from +60 km/s to -70 km/s in five bins ~ 25 km/s wide). We have found that the highest velocity and most highly collimated component, i.e. the jet, can be traced from DG Tau to a distance D ~ 0.7. The jet is on the axis of a pear-shaped limb-brightened bubble which extends between 0.4 and 1.5 from the source and which we interpret as a bow shock. Other condensations are seen close to the star indicating ongoing temporal variations in the flow. The low-velocity component of the outflow is found to be spatially wide close to the source (~ 0.2 at D=0.2), in contrast to the high velocity jet (width <~ 0.1). We have also found evidence to suggest that the density increases longitudinally with proximity to the source and also laterally towards the flow axis. Thus, at least in the case of DG Tau, the flow becomes gradually denser as it increases in velocity and becomes more collimated. Our observations show a continous bracketing of the higher speed central flow within the lower speed, less collimated, broader flow, down to the lowest velocity scales. This suggests that the low and high velocity FELs in the highly active T Tauri star DG Tau are intimately related.
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