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Analytic gas orbits in an arbitrary rotating galactic potential using the linear epicyclic approximation
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
2012 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 421, no 2, 1089-1102 p.Article in journal (Refereed) Published
Abstract [en]

A code, EPIC5, has been developed which computes, in the two-dimensional case, the initially circular orbits of guiding centra in an arbitrary axisymmetric potential with an arbitrary, weak perturbing potential in solid body rotation. This perturbing potential is given by its Fourier expansion. The analytic solution solves the linear epicyclic approximation of the equations of motion. To simulate the motion of interstellar matter and to damp the Lindblad resonances, in these equations we have introduced a friction which is proportional to the deviation from circular velocity. The corotation resonance is also damped by a special parameter. The program produces, in just a few seconds, orbital and density maps, as well as line-of-sight velocity maps for a chosen orientation of the galaxy. We test EPIC5 by comparing its results with previous simulations and observations from the literature, which gives satisfactory agreement. The aim is that this program should be a useful complement to elaborate numerical simulations. Particularly so are its abilities to quickly explore the parameter space, to construct artificial galaxies and to isolate various single agents important for developing the structure of interstellar matter in disc galaxies. The EPIC5 code can be obtained from npi@astro.su.se.

Place, publisher, year, edition, pages
2012. Vol. 421, no 2, 1089-1102 p.
Keyword [en]
galaxies: kinematics and dynamics, galaxies: spiral
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-76054DOI: 10.1111/j.1365-2966.2011.20367.xISI: 000302695600013OAI: oai:DiVA.org:su-76054DiVA: diva2:525602
Note
3Available from: 2012-05-08 Created: 2012-05-08 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Rearrangement of gas in disc galaxies
Open this publication in new window or tab >>Rearrangement of gas in disc galaxies
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Active galactic nuclei and bursts of star formation are two distinct phenomena that amply change their host environments. They are present in a significant number of galaxies at all redshifts. In this thesis, we aim toward a better understanding of the physical processes that allow for the formation and maintenance of these two phenomena. We focus on the study of the physical conditions of the interstellar gas in the central kiloparsec region of the barred active galaxy NGC 1097 (Paper I). In Paper I we present different CO transitions and the consequent analysis realized in order to derive the molecular gas content together with the molecular mass inflow toward the centre of the galactic gravitational potential well. To completely understand the physical processes that drive such gas rearrangement, a coherent picture for a dynamical system has to be considered. We have developed a code, Paper II, in order to model the dynamics of a predominantly rotating system with an arbitrary mass distribution. The formalism we have used is based on analytical solutions of the first order approximation of the equations of motion of a smooth medium that may be subject to dissipation. The most important free parameter to constrain the boundary conditions of the model is the angular frequency of the perturbing pattern, which may be assumed virtually invariant over significant ranges of galactocentric radii. We constrain the pattern velocity using the Tremaine-Weinberg method (Paper III). Hence, we have prepared all procedures needed to comprehend the physical processes that sustain the nuclear activity and bursts of star formation: the amount of gas in the region and the dynamics of the system. In Paper IV, we model the neutral and ionized gas kinematics in NGC 1097 and apply a combination of the methods described in Paper II and Paper III to comprehend the rearrangement of gas in the galaxy. In order to observationally discern the gas inflow in the nuclear region at a higher resolution, we apply the methods developed and used in this thesis to Cycle-0 ALMA observations of our target galaxy, and we confirm that we are able to follow the streaming of gas from 20 kiloparsec distances down to 40 parsecs from its central central supermassive black hole (Paper V).

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University, 2013. 54 p.
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-88636 (URN)978-91-7447-673-6 (ISBN)
Public defence
2013-06-05, sal FB52, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Submitted.

Available from: 2013-05-14 Created: 2013-03-23 Last updated: 2013-04-25Bibliographically approved

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