Kinematical investigation of possible fast collimated outflows in twelve planetary nebulae

ABSTRACT A significant fraction of planetary nebulae (PNe) exhibit collimated outflows, distinct narrow kinematical components with notable velocity shifts with respect to the main nebular shells typically associated with low-ionization compact knots and linear or precessing jet-like features. We present here a spatio-kinematical investigation of a sample of 12 PNe with morphologies in emission lines of low-ionization species suggestive of collimated outflows. Using archival narrow-band images and our own high-dispersion long-slit echelle spectra, we confirm the presence of collimated outflows in Hen 2-429, J 320, M 1-66, M 2-40, M 3-1, and NGC 6210 and possibly in NGC 6741, for which the spatio-kinematical data can also be interpreted as a pair of bipolar lobes. The presence of collimated outflows is rejected in Hen 2-47, Hen 2-115, M 1-26, and M 1-37, but their morphology and kinematics are indicative of the action of supersonic outflows that have not been able to pierce through the nebular envelope. In this sense, M 1-66 appears to have experienced a similar interaction between the outflow and nebular envelope, but, as opposed to these four PNe, the outflow has been able to break through the nebular envelope. It is suggested that the PNe without collimated outflows in our sample are younger or descend from lower mass progenitors than those that exhibit unambiguous collimated outflows.

On the Possibility of Applying the Quasi-Isothermal Stäckel’s Model to Our Galaxy

An earlier derived quasi-isothermal Stäckel’s model of mass distribution in stellar systems and the corresponding formula for space density are applied to our Galaxy. The model rotation curve is fitted to HI kinematical data. The structural and scale parameters of the model are estimated and the corresponding density contours for our Galaxy are presented.

Massive Elliptical Galaxies: BH Scouring or a Bottom-Heavy IMF?

We present indirect constraints on the stellar initial-mass-function (IMF) in nine massive elliptical galaxies with σ ≈ 300 km/s, via a comparison of dynamical and stellar-population based stellar masses. We use adaptive-optics assisted, high resolution kinematical data from the SINFONI Search for Supermassive Black Holes that allow us to constrain the dynamical stellar mass-to-light ratio in the very centre of each galaxy. Hence we measure the IMF in a galaxy region where the stellar mass dominates over dark matter, minimising any potential degeneracy between the two mass components. In six of our galaxies – those which have depleted stellar cores – we find an IMF consistent with the one measured in the Milky-Way via direct star counts. The three remaining, power-law galaxies have instead stellar masses about a factor of two times larger than expected from a Milky-Way type IMF, indicating either a more bottom-heavy IMF (like, e.g., the Salpeter IMF) or a dark-matter distribution that is degenerate with the stellar mass down to the very centres of these galaxies. The bottom-light IMF in our core galaxies is surprising in view of previous studies that suggested a systematic IMF variation where early-type galaxies with σ ≈ 300 km/s have a Salpeter or even more dwarf-dominated IMF. Core galaxies are particularly important since their unique central orbital structure offers an independent crosscheck for the dynamical models. Our models with a bottom-light IMF are consistent with the distribution of orbits predicted by SMBH-binary core-formation models. This indicates that spatially well resolved central kinematical data are important for determining unbiased dynamical stellar mass-to-light ratios. Our results imply either that the IMF in massive galaxies varies over a wider range than previously anticipated, and is not the same in core and power-law ellipticals, or else that there are systematic variations in the distribution of dark matter among massive early-type galaxies.

Properties of satellite galaxies in nearby groups

We studied the variation of stellar mass and various star-formation characteristics of satellite galaxies in a volume limited sample of nearby groups as a function of their group-centric distance and of their relative line-of-sight velocity in the group rest frame. We found clear radial dependencies, e.g. massive, red and passive satellites being distributed predominantly near the center of composite group. We also found some evidence of velocity modulation of star-forming properties of satellite galaxies near the group virial radius. We conclude that using kinematical data, it should be feasible to separate dynamical classes of bound, in-falling and 'backsplash' satellite galaxies.

The global dark halo structure of the Andromeda galaxy

We set new limits on the global shape of the dark halo in the Andromeda galaxy based on axisymmetric mass models constructed by Hayashi & Chiba (2012). This is motivated by the fact that CDM models predict non-spherical virialized dark halos, which reflect the process of mass assembly in the galactic scale. Based on the application of our models to latest kinematical data of globular clusters and dwarf spheroidal galaxies in the Andromeda halo, we find that the most plausible cases for Andromeda yield not a spherical but a prolate shape for its dark halo. We also find that the prolate dark halo is consistent with theoretical predictions in which the satellites are distributed anisotropically and preferentially located along major axes of their galactic host halos. It is a reflection of the intimate connection between galactic dark matter halos and the cosmic web.

STRUCTURES OUT OF CHAOS IN BARRED-SPIRAL GALAXIES

We review the dynamical mechanisms we have found to support the morphological features in barred-spiral galaxies based on chaotic motions of stars in their gravitational fields. These morphological features are the spiral arms, that emerge out of the ends of the bar, but also shape the bar itself. The potentials used have been estimated directly from near-infrared images of barred-spiral galaxies. In this paper, we present the results from the study of the dynamics of the potentials of the galaxies NGC 4314, NGC 1300 and NGC 3359. The main unknown parameter in our models is the pattern speed of the system Ωp. By varying Ωp, we have investigated several cases trying to match the results of our modeling with available photometrical and kinematical data. We found realistic models with stars on spirals in chaotic motion, while their bars are built by stars usually on regular orbits. However, we also encountered cases, where a major part of trajectories of the stars even in the bar is chaotic as well. Finally, we examined the gas dynamics of barred-spiral systems, and found that the presence of gas reinforces the intensity of the "chaotic" spiral arms.

Expansion velocities of selected PNe

In order to clarify the observed relation between the expansion velocity measured from lines of different ions and their ionization potential, we present kinematical data for several objects. We have measured radial velocities on ESO UVES high dispersion spectra to compare expansion velocities for a set of planetary nebulae.