Dynamics of elliptical and bulge galaxies using planetary nebulae
Date
2011
Authors
Moylan, E. K. M.
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
We explore the dynamics of four elliptical and bulge galaxies. We focus on the outer parts where the mass is dark-matter dominated and the orbital structures describe the formation histories. We combined the measured kinematics of planetary nebulae (PN) with integrated light kinematics and photometry to provide a radially complete set of compatible observational constraints. The sample is comprised of NGC 1399, NGC 3923, NGC 1316 and NGC 4594. NGC 1399 is one of the nearest cD galaxies and is an archetypal, slow-rotating, giant elliptical. NGC 3923 has a spectacular system of 22 shells left over from a merger. NGC 1316 is the brightest cluster galaxy in Fornax and is a recent merger remnant. NGC 4594 (M104, Sombrero) has a large bulge and a nearly edge-on dusty disk. In each case, we study the rotation and dispersion profile of the kinematic tracers. For the first three galaxies, we explore the dark matter content and the orbital structure using dynamical models.
We generated four PN velocity catalogs plus a catalog of PNe in NGC 1317. The kinematics of the four galaxies describe the varied formation histories of the sample. The marginal rotation in NGC 1399 contrasts with the clear rotation signal in NGC 1316. The PN in NGC 4594 confirm observations of non-cylindrical rotation. Rotation in the outer parts of NGC 3923 is surprising given the alignment and regularity of the shell system. The halo dispersion profiles range from gently rising in NGC 3923 to steeply falling in NGC 1316.
We performed Jeans modeling of NGC 3923 and NGC 1316 and applied the made-to-measure N-body code, NMAGIC, to NGC 1399. All of our models require dark matter in the outer parts in order to fit the observed PN kinematics. Comparing the models and observations, we use the four galaxies in this sample to learn about the formation and evolution of elliptical and bulge galaxies. Based on this sample, we find that very evolved systems like cD galaxies have triaxial distributions and marginal rotation. In contrast, NGC 1316, the dominant galaxy in its subcluster, shows very different dynamics: strong rotation and an axisymmetric distribution. Clearly the later stages of hierarchical assembly have a big impact on the dynamics of early-type galaxies. Our observations of NGC 3923 indicate that shells around galaxies can be formed in less restricted circumstances than previously thought (Hernquist & Quinn 1989) and they are robust. Bulge galaxies have characteristics in common with both elliptical and disk galaxies. The rotation of the PN sample in NGC 4594 underscores the impact of scale on the classification of these objects - near the disk the bulge rotates strongly, but in the outer parts it has more in common with an elliptical. Dark matter composes between 5% and 31% of the total mass within 1 R{u212F}. The transition to dark matter dominance occurs in the range of 2-4 R{u212F}, in agreement with the result from Gerhard et al. (2001).
Description
Keywords
Citation
Collections
Source
Type
Thesis (PhD)
Book Title
Entity type
Access Statement
Open Access
License Rights
Restricted until
Downloads
File
Description