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Title:
Kinematic Evidence for Halo Substructure in Spiral Galaxies
Authors:
Herrmann, Kimberly A.; Ciardullo, Robin; Sigurdsson, Steinn
Affiliation:
AA(Visiting Astronomer, Cerro Tololo Inter-American Observatory. CTIO is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under contract to the National Science Foundation. ; Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatories, which is operated by AURA under cooperative agreement with the National Science Foundation. The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatories. ; Current address: Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ, 86001, USA.), AB(Visiting Astronomer, Cerro Tololo Inter-American Observatory. CTIO is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under contract to the National Science Foundation. ; Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatories, which is operated by AURA under cooperative agreement with the National Science Foundation. The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatories. ), AC(Department of Astronomy & Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA )
Publication:
The Astrophysical Journal Letters, Volume 693, Issue 1, pp. L19-L22 (2009). (ApJL Homepage)
Publication Date:
03/2009
Origin:
IOP
ApJ Keywords:
galaxies: individual: NGC 5236 NGC 4736, galaxies: kinematics and dynamics, galaxies: spiral, planetary nebula: general
DOI:
10.1088/0004-637X/693/1/L19
Bibliographic Code:
2009ApJ...693L..19H

Abstract

We present the results of a kinematic study of planetary nebulae in the extreme outskirts of two spiral galaxies, M83 (NGC 5236) and M94 (NGC 4736). We find that in the inner regions of the galaxies, the vertical velocity dispersion (σ z ) falls off exponentially with the light, as expected for a constant mass-to-light ratio, constant thickness disk. However, starting at four optical scale lengths, σ z asymptotes out at roughly 20 km s-1. Our analysis finds evidence for significant flaring in the outer regions as well, especially in M94. These observations are in excellent agreement with predictions derived from models of disk heating by halo substructure, and demonstrate how kinematic surveys in the outer disks of spirals can be used to test hierarchical models of galaxy formation.
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