Kinematic evidence for halo substructure in spiral galaxies

Research output: Contribution to journalArticle

14 Citations (Scopus)

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 (σz) 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, σz 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.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume693
Issue number1 PART 2
DOIs
StatePublished - Jan 1 2009

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spiral galaxies
substructures
halos
kinematics
mass to light ratios
asymptotes
planetary nebulae
galactic evolution
heating
prediction
galaxies
predictions
flaring
analysis
test

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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title = "Kinematic evidence for halo substructure in spiral galaxies",
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 (σz) 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, σz 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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Kinematic evidence for halo substructure in spiral galaxies. / Herrmann, Kimberly A.; Ciardullo, Robin; Sigurdsson, Steinn.

In: Astrophysical Journal, Vol. 693, No. 1 PART 2, 01.01.2009.

Research output: Contribution to journalArticle

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T1 - Kinematic evidence for halo substructure in spiral galaxies

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AU - Ciardullo, Robin

AU - Sigurdsson, Steinn

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AB - 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 (σz) 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, σz 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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