Search

Using VLT/MUSE integral-field spectroscopic data for the barred spiral galaxy NGC 1097, we explore techniques that can be used to search for extended coherent shocks that can drive gas inflows in centres of galaxies. Such shocks should appear as coherent velocity jumps in gas kinematic maps, but this appearance can be distorted by inaccurate extraction of the velocity values and dominated by the global rotational flow and local perturbations like stellar outflows. We include multiple components in the emission-line fits, which corrects the extracted velocity values and reveals emission associated with AGN outflows. We show that removal of the global rotational flow by subtracting the circular velocity of a fitted flat disk can produce artefacts that obscure signatures of the shocks in the residual velocities if the inner part of the disk is warped or if gas is moving around the centre on elongated (non-circular) trajectories. As an alternative, we propose a model-independent method which examines differences in the LOSVD moments of H$\alpha$ and [N II]$\lambda$6583. This new method successfully reveals the presence of continuous shocks in the regions inward from the nuclear ring of NGC 1097, in agreement with nuclear spiral models., Comment: MNRAS accepted (19 pages, 18 figures, 1 table)

The $M_{BH}$ - $��_{\star}$ relation is considered a result of co-evolution between the host galaxies and their super-massive black holes. For elliptical-bulge hosting inactive galaxies, this relation is well established, but there is still a debate whether active galaxies follow the same relation. In this paper, we estimate black hole masses for a sample of 19 local luminous AGNs (LLAMA) in order to test their location on the $M_{BH}$ - $��_{\star}$ relation. Super-massive black hole masses ($M_{BH}$) were derived from the broad-line based relations for H$��$, H$��$ and Pa$��$ emission line profiles for the Type 1 AGNs. We compare the bulge stellar velocity dispersion ($��_{\star}$) as determined from the Ca II triplet (CaT) with the dispersion measured from the near-infrared CO (2-0) absorption features for each AGN and find them to be consistent with each other. We apply an extinction correction to the observed broad line fluxes and we correct the stellar velocity dispersion by an average rotation contribution as determined from spatially resolved stellar kinematic maps. The H$��$-based black hole masses of our sample of AGNs were estimated in the range 6.34 $\leq$ $\log{M_{BH}}$ $\leq$ 7.75 M$_\odot$ and the $��_{\star CaT}$ estimates range between 73 $\leq$ $��_{\star CaT}$ $\leq$ 227 km s$^{-1}$. From the so-constructed $M_{BH}$ - $��_{\star}$ relation for our Type 1 AGNs, we estimate the black hole masses for the Type 2 AGNs and the inactive galaxies in our sample. In conclusion, we find that our sample of local luminous AGNs is consistent with the $M_{BH}$ - $��_{\star}$ relation of lower luminosity AGNs and inactive galaxies, after correcting for dust extinction and the rotational contribution to the stellar velocity dispersion., Accepted by A&A, 30 pages, 19 figures

The backbone of double bars is made out of double-frequency orbits, and loops, their maps, indicate the bars' extent, morphology and dynamics., 2 pages, 1 figure; to appear in "Formation and Evolution of Galaxy Disks", ASP Conf. Ser., eds. J.G. Funes & E.M. Corsini

We report on our attempts to achieve a nearly steady-state gas flow in hydrodynamical simulations of doubly barred galaxies. After exploring the parameter space, we construct two models, for which we evaluate the photometric and the kinematic integrals, present in the Tremaine-Weinberg method, in search of observational signatures of two rotating patterns. We show that such signatures are often present, but a direct fit to data points is likely to return incorrect pattern speeds. However, for a particular distribution of the tracer, presented here, the values of the pattern speeds can be retrieved reliably even with the direct fit., 4 pages, 2 figures; to appear in "Formation and Evolution of Galaxy Disks", ASP Conf. Ser., eds. J.G. Funes & E.M. Corsini

Bars in galaxies are mainly supported by particles trapped around stable periodic orbits. These orbits represent oscillatory motion with only one frequency, which is the bar driving frequency, and miss free oscillations. We show that a similar situation takes place in double bars: particles get trapped around parent orbits, which in this case represent oscillatory motion with two frequencies of driving by the two bars, and which also lack free oscillations. Thus the parent orbits, which constitute the backbone of an oscillating potential of two independently rotating bars, are the double-frequency orbits. These orbits do not close in any reference frame, but they map onto loops, first introduced by Maciejewski & Sparke (1997). Trajectories trapped around the parent double-frequency orbit map onto a set of points confined within a ring surrounding the loop., 10 pages, 6 figures, submitted to MNRAS

When integrals in the standard Tremaine-Weinberg method are evaluated for the case of a realistic model of a doubly barred galaxy, their modifications introduced by the second rotating pattern are in accord with what can be derived from a simple extension of that method, based on separation of tracer's density. This extension yields a qualitative argument that discriminates between prograde and retrograde inner bars. However, the estimate of the value of inner bar's pattern speed requires further assumptions. When this extension of the Tremaine-Weinberg method is applied to the recent observation of the doubly barred galaxy NGC 2950, it indicates that the inner bar there is counter-rotating, possibly with the pattern speed of -140 +/- 50 km/s/arcsec. The occurrence of counter-rotating inner bars can constrain theories of galaxy formation., Comment: accepted by MNRAS; Appendix A added, Discussion expanded

Bars in galaxies are mainly supported by particles trapped around closed periodic orbits. These orbits respond to the bar's forcing frequency only and lack free oscillations. We show that a similar situation takes place in double bars: particles get trapped around orbits which only respond to the forcing from the two bars and lack free oscillations. We find that writing the successive positions of a particle on such an orbit every time the bars align generates a closed curve, which we call a loop. Loops allow us to verify consistency of the potential. As maps of doubly periodic orbits, loops can be used to search the phase-space in double bars in order to determine the fraction occupied by ordered motions., Comment: 10 pages, 5 figures, to appear in Lecture Notes in Physics, vol. "Galaxies and Chaos", eds. G. Contopoulos & N. Voglis

A wide-spread belief that nested bars enhance gas inflow to the galactic centre has recently been contradicted by dynamical models in which inner bars seem to prohibit such inflow. Can the existing models of dynamically possible double bars be modified to enable strong inflow in the secondary bar? I present here simple dynamical arguments which imply that in general, double bars in resonant coupling do not enhance gas inflow. However, stronger inflow with straight shocks in the inner bar can occur if there is no resonant coupling of the commonly assumed form between the bars., 4 pages, 1 figure, to appear in "Disks of Galaxies : Kinematics, Dynamics and Perturbations" (ASP Conference Series), eds E.Athanassoula and A.Bosma

With a help of hydrodynamical models, we explore fundamental modes of gas flow in central parts of a galaxy potential with non-axisymmetric perturbations of various strengths. Our grid-based algorithm allows us to get a detailed picture of gas dynamics down to about 10 pc from the galaxy center, where the central black hole becomes dominant. Gas inflow in a bar with an Inner Lindblad Resonance often stops at the nuclear ring. We find that embedded bars in resonant coupling are unlikely to increase the inflow, but for certain gas parameters in a single bar, inflow to the center develops in a spiral shock, similar to the patterns observed in nuclear discs of real galaxies. The spiral pattern persists for very weak non-axisymmetries of the potential., 6 pages, 4 figures, to appear in ``The central kpc of starbursts and AGN: the La Palma connection'', Eds. J.H. Knapen, et al., ASP conf. series, in press (2001)

Motivated by STIS observations of more than 50 nearby galactic nuclei, we consider long-slit emission-line spectra when the slit is wider than the instrumental PSF. The finite width of the slit generates complex patterns in the spectra that can have considerable diagnostic power if they are modeled with adequate sophistication. They allowed us to develop a new method for estimating the BH mass that gives fuller information and higher sensitivity to BH detection than traditional methods., Comment: 2 pages, 1 figure. To appear in ASP Conference Series "Galaxy Disks and Disk Galaxies", J.G. Funes S.J. and E.M. Corsini, eds

(shortened version) We show that many observations of W44, a supernova remnant in the galactic plane at a distance of about 2500 pc, are remarkably consistent with the simplest realistic model. The model remnant is evolving in a smooth ambient medium of fairly high density, about 6 cm^-3 on average, with a substantial density gradient. At the observed time it has an age of about 20,000 years, consistent with the age of the associated pulsar, and a radius of 11 to 13 pc. Over most of the outer surface, radiative cooling has become important in the post shock gas; on the denser end there has been sufficient compression of the cooled gas to develop a very thin dense half shell of about 450 M_sun, supported against further compression by nonthermal pressure. The half shell has an expansion velocity of about 150 km s^-1, and is bounded on the outer surface by a radiative shock with that speed. We provide several analytic tools for the assembly of models of this type. We review the early evolution and shell formation analyses and their generalizations to evolution in a density gradient. We also calculate the density and temperature that should be present in the hot interior of a remnant with thermal conduction. We supply the van der Laan mechanism in a particularly useful form for the calculation of radio continuum from radiative remnants. Finally, we demonstrate a simple technique for estimating the optical emission expected. These tools are employed to choose parameters of models which we then explore with our 1d and 2d hydrocodes, providing, respectively, the detailed x-ray spectra and dynamical characteristics., Comment: 42 pages, latex, uses a4wide.sty, 18 figures; original figures available at ftp://ftp.astro.wisc.edu/outgoing/witold/w44/ ; submitted to ApJ

Inner regions of barred disk galaxies often include asymmetrical, small-scale central features, some of which are best described as secondary bars. Because orbital timescales in the galaxy center are short, secondary bars are likely to be dynamically decoupled from the main kiloparsec-scale bars. We found that non-chaotic multiply-periodic particle orbits can exist in potentials with two dynamically decoupled bars.Stars trapped around these orbits could form the building blocks for a long-lived, doubly-barred galaxy. A self-consistent secondary bar appears to induce formation of inner gaseous rings rather than shocks in gas flow., Comment: 4 pages, including 1 figure, pasp style. To appear in the proceedings of "Galaxy Dynamics" conference held in Rutgers, August 1998