Modeling dark haloes in early-type galaxies: stellar kinematics at large radii

We developed a new method to obtain absorption line spectra of early-type galaxies at large radii, using integral-field spectrography (IFS). By using the spectrograph as a 'photon-collector' and adding the signal of many individual spaxels together in one spectrum, we obtain sufficient signal-to-noise to measure both stellar kinematics and line strengths at large radii. These can be used to determine the properties of the dark matter halo, as well as the stellar halo population.

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Origins of Stellar Halos

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315008753 ◽

2015 ◽

Vol 11 (S317) ◽

pp. 1-8

Author(s):

Kathryn V. Johnston

Keyword(s):

Dark Matter ◽

Milky Way ◽

Stellar Populations ◽

Observational Evidence ◽

Dark Matter Halo ◽

Theoretical Understanding ◽

Stellar Halo ◽

The One ◽

Halo Population

AbstractThis contribution reviews ideas about the origins of stellar halos. It includes discussion of the theoretical understanding of and observational evidence for stellar populations formed “in situ” (meaning formed in orbits close to their current ones), “kicked-out” (meaning formed in the inner galaxy in orbits unlike their current ones) and “accreted” (meaning formed in a dark matter halo other than the one they currently occupy). At this point there is general agreement that a significant fraction of any stellar halo population is likely “accreted”. There is modest evidence for the presence of a “kicked-out” population around both the Milky Way and M31. Our theoretical understanding of and the observational evidence for an “in situ” population are less clear.

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Mapping the dark matter halo of early-type galaxy NGC 2974 through orbit-based models with combined stellar and cold gas kinematics

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3293 ◽

2019 ◽

Vol 491 (3) ◽

pp. 4221-4231 ◽

Cited By ~ 5

Author(s):

Meng Yang ◽

Ling Zhu ◽

Anne-Marie Weijmans ◽

Glenn van de Ven ◽

Nicholas Boardman ◽

...

Keyword(s):

Dark Matter ◽

Dark Matter Halo ◽

Dark Halo ◽

Confidence Limits ◽

Early Type ◽

Stellar Kinematics ◽

Stellar Orbits ◽

Gas Kinematics ◽

Early Type Galaxy ◽

Cold Gas

ABSTRACT We present an orbit-based method of combining stellar and cold gas kinematics to constrain the dark matter profile of early-type galaxies. We apply this method to early-type galaxy NGC 2974, using Pan-STARRS imaging and SAURON stellar kinematics to model the stellar orbits, and introducing H i kinematics from VLA observation as a tracer of the gravitational potential. The introduction of the cold gas kinematics shows a significant effect on the confidence limits of especially the dark halo properties: we exclude more than $95{{\ \rm per\ cent}}$ of models within the 1σ confidence level of Schwarzschild modelling with only stellar kinematics, and reduce the relative uncertainty of the dark matter fraction significantly to $10{{\ \rm per\ cent}}$ within 5Re. Adopting a generalized Navarro–Frenk–White (NFW) dark matter profile, we measure a shallow cuspy inner slope of $0.6^{+0.2}_{-0.3}$ when including the cold gas kinematics in our model. We cannot constrain the inner slope with the stellar kinematics alone.

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The gravitational force field of the Galaxy measured from the kinematics of RR Lyrae in Gaia

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz572 ◽

2019 ◽

Vol 485 (3) ◽

pp. 3296-3316 ◽

Cited By ~ 26

Author(s):

Christopher Wegg ◽

Ortwin Gerhard ◽

Marie Bieth

Keyword(s):

Dark Matter ◽

Dark Matter Halo ◽

Galactic Centre ◽

Gravitational Acceleration ◽

Momentum Exchange ◽

Acceleration Field ◽

Rr Lyrae ◽

Halo Stars ◽

The Galaxy ◽

Stellar Halo

Abstract From a sample of 15651 RR Lyrae with accurate proper motions in Gaia DR2, we measure the azimuthally averaged kinematics of the inner stellar halo between 1.5 and 20 kpc from the Galactic centre. We find that their kinematics are strongly radially anisotropic, and their velocity ellipsoid nearly spherically aligned over this volume. Only in the inner regions ${\lesssim } 5\, {\rm kpc}\,$ does the anisotropy significantly fall (but still with β > 0.25) and the velocity ellipsoid tilt towards cylindrical alignment. In the inner regions, our sample of halo stars rotates at up to $50\, {\rm km}\, {\rm s}^{-1}\,$, which may reflect the early history of the Milky Way, although there is also a significant angular momentum exchange with the Galactic bar at these radii. We subsequently apply the Jeans equations to these kinematic measurements in order to non-parametrically infer the azimuthally averaged gravitational acceleration field over this volume, and by removing the contribution from baryonic matter, measure the contribution from dark matter. We find that the gravitational potential of the dark matter is nearly spherical with average flattening $q_\Phi ={1.01 \pm 0.06\, }$ between 5 and 20 kpc, and by fitting parametric ellipsoidal density profiles to the acceleration field, we measure the flattening of the dark matter halo over these radii to be $q_\rho ={1.00 \pm 0.09\, }\!.$

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Decoupling the rotation of stars and gas – I. The relationship with morphology and halo spin

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3575 ◽

2019 ◽

Vol 492 (2) ◽

pp. 1869-1886 ◽

Cited By ~ 8

Author(s):

Christopher Duckworth ◽

Rita Tojeiro ◽

Katarina Kraljic

Keyword(s):

Dark Matter ◽

Angular Momentum ◽

Group Membership ◽

Dark Matter Halo ◽

Early Type ◽

Late Type ◽

Crucial Step ◽

Fundamental Relationship ◽

Gas Loss ◽

The Relationship

ABSTRACT We use a combination of data from the MaNGA survey and MaNGA-like observations in IllustrisTNG100 to determine the prevalence of misalignment between the rotational axes of stars and gas. This census paper outlines the typical characteristics of misaligned galaxies in both observations and simulations to determine their fundamental relationship with morphology and angular momentum. We present a sample of ∼4500 galaxies from MaNGA with kinematic classifications which we use to demonstrate that the prevalence of misalignment is strongly dependent on morphology. The misaligned fraction sharply increases going to earlier morphologies (28 ± 3 per cent of 301 early-type galaxies, 10 ± 1 per cent of 677 lenticulars, and 5.4 ± 0.6 per cent of 1634 pure late-type galaxies). For early-types, aligned galaxies are less massive than the misaligned sample whereas this trend reverses for lenticulars and pure late-types. We also find that decoupling depends on group membership for early-types with centrals more likely to be decoupled than satellites. We demonstrate that misaligned galaxies have similar stellar angular momentum to galaxies without gas rotation, much lower than aligned galaxies. Misaligned galaxies also have a lower gas mass than the aligned, indicative that gas loss is a crucial step in decoupling star–gas rotation. Through comparison to a mock MaNGA sample, we find that the strong trends with morphology and angular momentum hold true in IllustrisTNG100. We demonstrate that the lowered angular momentum is, however, not a transient property and that the likelihood of star–gas misalignment at $z$ = 0 is correlated with the spin of the dark matter halo going back to $z$ = 1.

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Mapping the dark matter of NGC 2974: Combination of stellar & cold gas kinematics

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319008287 ◽

2019 ◽

Vol 14 (S353) ◽

pp. 253-254

Author(s):

M. Yang ◽

L. Zhu ◽

A. Weijmans ◽

G. van de Ven ◽

N. F. Boardman ◽

...

Keyword(s):

Dark Matter ◽

New Method ◽

Stellar Kinematics ◽

Gas Kinematics ◽

Superposition Technique ◽

Cold Gas

AbstractWe present a new method to combine cold gas kinematics with the stellar kinematics modelled with the Schwarzschild orbit-superposition technique, and its application to the lenticular galaxy NGC 2974. The combination of stellar and cold gas kinematics significantly improves the constraints on the measured dark matter profile: assuming a generalised NFW halo profile, we find a cuspy inner halo slope for NGC 2974.

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Globular Clusters in Early-Type Galaxies with GMOS

Highlights of Astronomy ◽

10.1017/s1539299600015501 ◽

2005 ◽

Vol 13 ◽

pp. 173-174

Author(s):

Terry Bridges ◽

Mike Beasley ◽

Favio Faifer ◽

Duncan Forbes ◽

Juan Forte ◽

...

Keyword(s):

Dark Matter ◽

Globular Clusters ◽

Velocity Dispersion ◽

Dark Matter Halo ◽

Early Type ◽

Color Distribution ◽

Local Mass

AbstractWe present recent results from our long-term Gemini/GMOS study of globular clusters (GCs) in early-type galaxies. To date, we have obtained photometry and spectroscopy for GCs in NGCs 3379, 4649, 524, 7332, and IC 1459. We find a clear bimodality in the NGC 4649 GC color distribution, with the fraction of blue/red clusters increasing with galacto-centric radius. We derive ages and metallicities for 22 GCs in NGC 3379, finding that most of the clusters appear old (10–15 Gyr); however, there is a group of 4 metal-rich, younger clusters with ages of 2–6 Gyr. The NGC 3379 GC velocity dispersion decreases with radius, as does the inferred (local) mass-to-light ratio: there is no evidence for a dark matter halo in NGC 3379 based on our GC data.

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Star Formation in Nearby Early-Type Galaxies: Mapping in UV, Optical and CO

Proceedings of the International Astronomical Union ◽

10.1017/s1743921306006697 ◽

2006 ◽

Vol 2 (S235) ◽

pp. 304-304

Author(s):

M. Bureau ◽

R. Bacon ◽

M. Cappellari ◽

F. Combes ◽

R. L. Davies ◽

...

Keyword(s):

Star Formation ◽

Field Survey ◽

Stellar Disk ◽

Early Type ◽

Stellar Kinematics ◽

Direct Identification ◽

Central Disk ◽

Co Detection ◽

Integral Field ◽

Fast Rotating

AbstractThe SAURON integral-field survey reveals that small (~0.1,Re) kinematically decoupled cores (KDCs) in early-type galaxies are increasingly young toward the center and are typically found in fast-rotating galaxies, while large KDCs (~0.5 Re) have homogeneously old stars and are present in non-rotating galaxies (McDermid et al. 2006). GALEX UV imaging further allows the direct identification of regions of recent star formation (≤0.5 Gyr). In NGC 2974 for example, young stars are identified in the center and an outer ring Jeong et al. 2006). Nuclear and inner ionised-gas rings (Sarzi et al. 2006) then suggest that current star formation is bar-driven. The CO detection rate of SAURON early-type galaxies is ≈40% (Combes et al. in prep.). Synthesis imaging reveals that it is generally contained in a well-ordered central disk, both in galaxies with a (young) central stellar disk (e.g. NGC 4459, NGC 4526) or a (young) KDC (e.g. NGC 3032, NGC 4150) (Young et al. in prep.). CO also traces well the young stellar populations and ionised gas distribution and kinematics, but in KDCs not always the stellar kinematics Emsellem et al. 2004; Sarzi et al. 2006; Kuntschner et al. 2006).

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Spatially Resolved Stellar Kinematics of the Ultra-diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, and Cold Dark Matter Halo Fits

The Astrophysical Journal ◽

10.3847/1538-4357/ab2914 ◽

2019 ◽

Vol 880 (2) ◽

pp. 91 ◽

Cited By ~ 24

Author(s):

Pieter van Dokkum ◽

Asher Wasserman ◽

Shany Danieli ◽

Roberto Abraham ◽

Jean Brodie ◽

...

Keyword(s):

Dark Matter ◽

Cold Dark Matter ◽

Dark Matter Halo ◽

Stellar Kinematics ◽

Spatially Resolved

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Dust and the observed dark matter content of galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900183615 ◽

2004 ◽

Vol 220 ◽

pp. 343-344 ◽

Cited By ~ 1

Author(s):

Maarten Baes ◽

Herwig Dejonghe ◽

Jonathan I. Davies

Keyword(s):

Dark Matter ◽

Interstellar Dust ◽

Optical Rotation ◽

Elliptical Galaxies ◽

Matter Content ◽

Dark Matter Halo ◽

Stellar Kinematics ◽

The Galaxy ◽

Dust Attenuation ◽

Radiative Transfer Modeling

Using detailed Monte Carlo radiative transfer modeling, we examine the effects of absorption and scattering by interstellar dust on the observed kinematics of galaxies. Our modeling results have a direct impact on the derivation of the properties of dark matter haloes around both elliptical and spiral galaxies. We find that interstellar dust has a very significant effect on the observed stellar kinematics of elliptical galaxies, in the way that it mimics the presence of a dark matter halo. Taking dust into account in kinematical modeling procedures can reduce or even eliminate the need for dark matter at a few effective radii. Dust profoundly affects the optical rotation curve and stellar kinematics of edge-on disc galaxies. This effect, however, is significantly reduced when the galaxy is more than a few degrees from strictly edge-on. These results demonstrate that dust attenuation cannot be invoked as a possible mechanism to reconcile the discrepancies between the observed shallow slopes of LSB galaxy rotation curves and the dark matter cusps found in CDM cosmological simulations.

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