Interstellar Gas and a Dark Disk

Kramer, Eric David; Randall, Lisa

doi:10.3847/0004-637x/829/2/126

Cited by 31 publications

(42 citation statements)

References 51 publications

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“…The second origin, the existence of disk dark matter was first postulated by Oort (Oort 1932) who used it to explain the vertical equilbrium of old stars in the Galactic disk. It has also been invoked to explain the flaring of the Galactic gas disk (Kalberla et al 2007) and has been included as a component of the Galactic disk in several studies (Kramer & Randall 2016;Fan et al 2013;Saburova & Zasov 2013). The origin of disk dark matter has not been extensively explored but studies suggest that it could have formed as a result of mergers with satellite galaxies in ΛCDM simulations (Read et al 2008).…”

Section: Discussionmentioning

confidence: 99%

Tracing the Dynamical Mass in Galaxy Disks Using H i Velocity Dispersion and Its Implications for the Dark Matter Distribution in Galaxies

Das

McGaugh

Ianjamasimanana

et al. 2020

ApJ

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We present a method to derive the dynamical mass of face-on galaxy disks using their neutral hydrogen (H i) velocity dispersion (σ H i ). We have applied the method to nearby, gas rich galaxies that have extended H i gas disks and have low inclinations. The galaxy sample includes 4 large disk galaxies; NGC628, NGC6496, NGC3184, NGC4214 and 3 dwarf galaxies DDO46, DDO63 and DDO187. We have used archival H i data from the THINGS and LITTLE THINGS surveys to derive the H i gas distributions and SPITZER mid-infrared images to determine the stellar disk mass distributions. We examine the disk dynamical and baryonic mass ratios in the extreme outer disks where there is H i gas but no visible stellar disk. We find that for the large galaxies the disk dynamical and H i gas mass surface densities are comparable in the outer disks. But in the smaller dwarf galaxies, for which the total H i gas mass dominates the baryonic mass i.e. M(HI)≥M(stars), the disk dynamical mass is much larger than the baryonic mass. For these galaxies there must either be a very low luminosity stellar disk which provides the vertical support for the H i gas disk or there is halo dark matter associated with their disks, which is possible if the halo has an oblate shape so that the inner part of the dark matter halo is concentrated around the disk. Our results are important for explaining the equilibrium of H i disks in the absence of stellar disks, and is especially important for gas rich, dwarf galaxies that appear to have significant dark matter masses associated with their disks.

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Section: Discussionmentioning

confidence: 99%

Tracing the Dynamical Mass in Galaxy Disks Using H i Velocity Dispersion and Its Implications for the Dark Matter Distribution in Galaxies

Das

McGaugh

Ianjamasimanana

et al. 2020

ApJ

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“…The values and uncertainties, both observational and estimated, for all components have been compiled from Refs. [10,12,13,32] where Σ DD is the surface density and h DD is the disk height. A thin DD aligned with the baryonic disk contributes an additional source of attractive potential, which pulls matter towards the midplane (see Section 2.2 of Ref.…”

Section: Local Matter Content: Baryons Halo Dm and A Thin Ddmentioning

confidence: 99%

Using Gaia DR2 to constrain local dark matter density and thin dark disk

Buch

Leung

Fan

2019

J. Cosmol. Astropart. Phys.

122

137

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We use stellar kinematics from the latest Gaia data release (DR2) to measure the local dark matter (DM) density ρ DM in a heliocentric cylinder of radius R = 150 pc and half-height z = 200 pc. We also explore the prospect of using our analysis to estimate the DM density in local substructure by setting constraints on the surface density and scale height of a thin dark disk aligned with the baryonic disk and formed due to dissipative dark matter self-interactions. Performing the statistical analysis within a Bayesian framework for three types of tracers, we obtain ρ DM = 0.016 ± 0.010 M /pc 3 for A stars; early G stars give a similar result, while F stars yield a significantly higher value. For a thin dark disk, A stars set the strongest constraint: excluding surface densities (5-12) M /pc 2 for scale heights below 100 pc with 95% confidence. The upper bound of this constraint implies ∼ < 1% of the Milky Way DM mass is present in a dissipative dark sector. Comparing our results with those derived using Tycho-Gaia Astrometric Solution (TGAS) data, we find that the uncertainty in our measurements of the local DM content is dominated by systematic errors that arise from assumptions of our dynamical analysis in the low z region. Furthermore, there will only be a marginal reduction in these uncertainties with more data in the Gaia era. We comment on the robustness of our method and discuss potential improvements for future work.

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“…at R , by Marasco et al (2017). These latter also estimated σ HI /σ H 2 ≈ 0.5 within R , thus we decided to assign σ HI = 8±2 km s −1 and σ H 2 = 4±1 km s −1 to all radii beyond R , which are tipical values for the atomic and the molecular phases (see Kramer & Randall 2016 and references therein).…”

Section: Beyond the Solar Circlementioning

confidence: 99%

“…The agreement between the two determinations is remarkable and significantly consolidates our results. In the right panel, we show different ρ gas taken from the exhaustive collection in Kramer & Randall (2016), who provide the volume densities of the atomic and the molecular gas by Burton & Gordon (1978) and Nakanishi & Sofue (2003 (the uncertainties are unfortunately not available), and from Marasco et al (2017). All the points in Fig.…”

Section: Appendix C: Vsf Law With Alternative Determinations From Thementioning

confidence: 99%

The volumetric star formation law in the Milky Way

Fraternali

Pezzulli

Marasco

et al. 2019

A&A

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Several open questions on galaxy formation and evolution have their roots in the lack of a universal star formation law, that could univocally link the gas properties, e.g. its density, to the star formation rate (SFR) density. In a recent paper, we used a sample of nearby disc galaxies to infer the volumetric star formation (VSF) law, a tight correlation between the gas and the SFR volume densities derived under the assumption of hydrostatic equilibrium for the gas disc. However, due to the dearth of information about the vertical distribution of the SFR in these galaxies, we could not find a unique slope for the VSF law, but two alternative values. In this paper, we use the scale height of the SFR density distribution in our Galaxy adopting classical Cepheids (age 200 Myr) as tracers of star formation. We show that this latter is fully compatible with the flaring scale height expected from gas in hydrostatic equilibrium. These scale heights allowed us to convert the observed surface densities of gas and SFR into the corresponding volume densities. Our results indicate that the VSF law ρ SFR ∝ ρ α gas with α ≈ 2 is valid in the Milky Way as well as in nearby disc galaxies.

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Interstellar Gas and a Dark Disk

Cited by 31 publications

References 51 publications

Tracing the Dynamical Mass in Galaxy Disks Using H i Velocity Dispersion and Its Implications for the Dark Matter Distribution in Galaxies

Tracing the Dynamical Mass in Galaxy Disks Using H i Velocity Dispersion and Its Implications for the Dark Matter Distribution in Galaxies

Using Gaia DR2 to constrain local dark matter density and thin dark disk

The volumetric star formation law in the Milky Way

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