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Understanding the shape and diversity of dwarf galaxy rotation curves in ΛCDM

Read, J. I. ; Iorio, G. ; Agertz, O. LU and Fraternali, F. (2016) In Monthly Notices of the Royal Astronomical Society 462(4). p.3628-3645
Abstract

The shape and diversity of dwarf galaxy rotation curves is at apparent odds with dark matter halos in a Λ Cold Dark Matter (ΛCDM) cosmology. We use mock data from isolated dwarf galaxy simulations to show that this owes to three main effects. Firstly, stellar feedback heats dark matter, leading to a `coreNFW' dark matter density profile with a slowly rising rotation curve. Secondly, if close to a recent starburst, large H i bubbles push the rotation curve out of equilibrium, deforming the rotation curve shape. Thirdly, when galaxies are viewed near face-on, their best fit inclination is biased high. This can lead to a very shallow rotation curve that falsely implies a large dark matter core. All three problems can be avoided, however,... (More)

The shape and diversity of dwarf galaxy rotation curves is at apparent odds with dark matter halos in a Λ Cold Dark Matter (ΛCDM) cosmology. We use mock data from isolated dwarf galaxy simulations to show that this owes to three main effects. Firstly, stellar feedback heats dark matter, leading to a `coreNFW' dark matter density profile with a slowly rising rotation curve. Secondly, if close to a recent starburst, large H i bubbles push the rotation curve out of equilibrium, deforming the rotation curve shape. Thirdly, when galaxies are viewed near face-on, their best fit inclination is biased high. This can lead to a very shallow rotation curve that falsely implies a large dark matter core. All three problems can be avoided, however, by a combination of improved mass models and a careful selection of target galaxies. Fitting our coreNFW model to mock rotation curve data, we show that we can recover the rotation curve shape, dark matter halo mass M200 and concentration parameter c within our quoted uncertainties.We fit our coreNFW model to real data for four isolated dwarf irregulars, chosen to span a wide range of rotation curve shapes. We obtain an excellent fit for NGC 6822 and WLM, with tight constraints on M200, and c consistent with ΛCDM. However, IC 1613 and DDO 101 give a poor fit. For IC 1613, we show that this owes to disequilibria and its uncertain inclination i; for DDO 101, it owes to its uncertain distance D. If we assume iIC1613 ~ 15° and DDDO101 ~ 12 Mpc, consistent with current uncertainties, we are able to fit both galaxies very well. We conclude that ΛCDM appears to give an excellent match to dwarf galaxy rotation curves.

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Please use this url to cite or link to this publication:
author
; ; and
publishing date
type
Contribution to journal
publication status
published
keywords
Dark matter, Galaxies: dwarf, Galaxies: haloes, Galaxies: kinematics and dynamics
in
Monthly Notices of the Royal Astronomical Society
volume
462
issue
4
pages
18 pages
publisher
Oxford University Press
external identifiers
  • scopus:84994498914
ISSN
0035-8711
DOI
10.1093/mnras/stw1876
language
English
LU publication?
no
id
d8b5a5b5-d603-43be-94bd-9f91a315dfcd
date added to LUP
2019-02-07 11:13:52
date last changed
2022-04-25 21:15:52
@article{d8b5a5b5-d603-43be-94bd-9f91a315dfcd,
  abstract     = {{<p>The shape and diversity of dwarf galaxy rotation curves is at apparent odds with dark matter halos in a Λ Cold Dark Matter (ΛCDM) cosmology. We use mock data from isolated dwarf galaxy simulations to show that this owes to three main effects. Firstly, stellar feedback heats dark matter, leading to a `coreNFW' dark matter density profile with a slowly rising rotation curve. Secondly, if close to a recent starburst, large H i bubbles push the rotation curve out of equilibrium, deforming the rotation curve shape. Thirdly, when galaxies are viewed near face-on, their best fit inclination is biased high. This can lead to a very shallow rotation curve that falsely implies a large dark matter core. All three problems can be avoided, however, by a combination of improved mass models and a careful selection of target galaxies. Fitting our coreNFW model to mock rotation curve data, we show that we can recover the rotation curve shape, dark matter halo mass M<sub>200</sub> and concentration parameter c within our quoted uncertainties.We fit our coreNFW model to real data for four isolated dwarf irregulars, chosen to span a wide range of rotation curve shapes. We obtain an excellent fit for NGC 6822 and WLM, with tight constraints on M<sub>200</sub>, and c consistent with ΛCDM. However, IC 1613 and DDO 101 give a poor fit. For IC 1613, we show that this owes to disequilibria and its uncertain inclination i; for DDO 101, it owes to its uncertain distance D. If we assume i<sub>IC1613</sub> ~ 15° and D<sub>DDO101</sub> ~ 12 Mpc, consistent with current uncertainties, we are able to fit both galaxies very well. We conclude that ΛCDM appears to give an excellent match to dwarf galaxy rotation curves.</p>}},
  author       = {{Read, J. I. and Iorio, G. and Agertz, O. and Fraternali, F.}},
  issn         = {{0035-8711}},
  keywords     = {{Dark matter; Galaxies: dwarf; Galaxies: haloes; Galaxies: kinematics and dynamics}},
  language     = {{eng}},
  month        = {{11}},
  number       = {{4}},
  pages        = {{3628--3645}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{Understanding the shape and diversity of dwarf galaxy rotation curves in ΛCDM}},
  url          = {{http://dx.doi.org/10.1093/mnras/stw1876}},
  doi          = {{10.1093/mnras/stw1876}},
  volume       = {{462}},
  year         = {{2016}},
}