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

Read, JI, Iorio, G, Agertz, O and Fraternali, F (2016) Understanding the shape and diversity of dwarf galaxy rotation curves in LCDM Monthly Notices of the Royal Astronomical Society, 462 (4). pp. 3628-3645.

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Abstract

The shape and wide diversity of dwarf galaxy rotation curves is at apparent odds with dark matter halos in LCDM. We generate mock rotation curve data from dwarf galaxy simulations to show that this owes to bursty star formation driven by stellar feedback. There are three main effects. Firstly, stellar feedback transforms dark matter cusps into cores. Ignoring such transformations leads to a poor fit of the rotation curve shape and a large systematic bias on the halo concentration parameter c. Secondly, if close to a recent starburst, large HI bubbles push the rotation curve out of equilibrium. This makes the gas rotational velocity a poor probe of the underlying potential, leading to a systematic error on the halo virial mass M200 of up to half a dex. Thirdly, when galaxies are viewed near face-on (i<40deg), it is challenging to properly correct for their inclination i. This leads to a very shallow rotation curve, with a systematic underestimate of M200 of over a dex. All three problems can be easily avoided, however. Using a new coreNFW profile that accounts for cusp-core transformations, we show that we are able to successfully recover the rotation curve shape; dark matter halo mass M200; and concentration parameter c within our quoted uncertainties, provided that the galaxy is close to equilibrium. We fit our coreNFW model to four dwarf irregulars chosen to span a range of rotation curve shapes. We obtain an excellent fit for NGC 6822 and WLM. However, IC 1613 and DDO 101 give a poor fit. For IC 1613, this owes to disequilibria and its uncertain inclination; for DDO 101, the problem is its uncertain distance. Assuming i_IC1613 ~ 15deg and D_DDO101 ~ 12Mpc, we are able to fit both galaxies very well. We conclude that, once we avoid disequilibrium galaxies, or those with poorly measured inclination and/or distance, LCDM gives a remarkable match to dwarf galaxy rotation curves.

Item Type: Article
Subjects : Physics
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
AuthorsEmailORCID
Read, JIUNSPECIFIEDUNSPECIFIED
Iorio, GUNSPECIFIEDUNSPECIFIED
Agertz, OUNSPECIFIEDUNSPECIFIED
Fraternali, FUNSPECIFIEDUNSPECIFIED
Date : 30 July 2016
Copyright Disclaimer : This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Understanding the shape and diversity of dwarf galaxy rotation curves in {Lambda}CDM J. I. Read; G. Iorio; O. Agertz; F. Fraternali Monthly Notices of the Royal Astronomical Society 2016; doi: 10.1093/mnras/stw1876 is available online at: http://mnras.oxfordjournals.org/content/462/4/3628
Uncontrolled Keywords : astro-ph.GA, astro-ph.GA, galaxies: dwarf, galaxies: haloes, galaxies: kinematics and dynamics, cosmology: dark matter.
Related URLs :
Depositing User : Symplectic Elements
Date Deposited : 29 Jul 2016 11:49
Last Modified : 06 Sep 2016 08:46
URI: http://epubs.surrey.ac.uk/id/eprint/811565

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