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

Das, Mousumi; McGaugh, Stacy S.; Ianjamasimanana, Roger; Schombert, James M.; Dwarakanath, K. S.

doi:10.3847/1538-4357/ab5fcd

Cited by 32 publications

(46 citation statements)

References 80 publications

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“…One consequence of stronger self-gravity is a thinner disc at fixed σz, or equivalently larger σz at fixed thickness. Observational evidence for the latter was found by Das et al (2020). We also mention that only NLG has strong flaring in the outskirts in the more reliable 5 million particle models.…”

Section: Discussionmentioning

confidence: 56%

“…The development of a bar could be inhibited by heating up the disc, which would involve a Toomre parameter Q > 1. Our nominal LPH models use Q = 1.5, but observationally there is some evidence that galaxy discs are dynamically overheated in the ΛCDM context such that higher values are appropriate (Fuchs 2003;Saburova 2011;Das et al 2020). A dynamically overheated disc with Q = 2 was able to suppress the bar instability in an idealised CDM-based Newtonian simulation of M33 (section 4.3 of Sellwood et al 2019).…”

Section: Higher Toomre Parameter In the Lph Modelmentioning

confidence: 95%

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Barred spiral galaxies in modified gravity theories

Roshan

Banik

Ghafourian

et al. 2021

Monthly Notices of the Royal Astronomical Society

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When bars form within galaxy formation simulations in the standard cosmological context, dynamical friction with dark matter (DM) causes them to rotate rather slowly. However, almost all observed galactic bars are fast in terms of the ratio between corotation radius and bar length. Here, we explicitly display an 8σ tension between the observed distribution of this ratio and that in the EAGLE simulation at redshift 0. We also compare the evolution of Newtonian galactic discs embedded in DM haloes to their evolution in three extended gravity theories: Milgromian Dynamics (MOND), a model of non-local gravity, and a scalar-tensor-vector gravity theory (MOG). Although our models start with the same initial baryonic distribution and rotation curve, the long-term evolution is different. The bar instability happens more violently in MOND compared to the other models. There are some common features between the extended gravity models, in particular the negligible role played by dynamical friction − which plays a key role in the DM model. Partly for this reason, all extended gravity models predict weaker bars and faster bar pattern speeds compared to the DM case. Although the absence of strong bars in our idealized, isolated extended gravity simulations is in tension with observations, they reproduce the strong observational preference for ‘fast’ bar pattern speeds, which we could not do with DM. We confirm previous findings that apparently ‘ultrafast’ bars can be due to bar-spiral arm alignment leading to an overestimated bar length, especially in extended gravity scenarios where the bar is already fast.

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Section: Discussionmentioning

confidence: 56%

Section: Higher Toomre Parameter In the Lph Modelmentioning

confidence: 95%

Barred spiral galaxies in modified gravity theories

Roshan

Banik

Ghafourian

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…At these radii, it can play a significant role in regulating star formation by modulating the volume density and/or by providing the mass required to produce gravitational instabilities (see, e.g. Das et al 2020).…”

Section: Resultsmentioning

confidence: 99%

Theoretical modelling of two-component molecular discs in spiral galaxies

Patra

2020

A&A

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As recent observations of the molecular discs in spiral galaxies point to the existence of a diffuse, low-density thick molecular disc along with the prominent thin one, we investigate the observational signatures of this thick disc by theoretically modelling two-component molecular discs in a sample of eight nearby spiral galaxies. Assuming a prevailing hydrostatic equilibrium, we set up and solved the joint Poisson’s-Boltzmann equation to estimate the three-dimensional distribution of the molecular gas and the molecular scale height in our sample galaxies. The molecular scale height in a two-component molecular disc is found to vary between 50 and 300 pc, which is higher than what is found in a single-component disc. We find that this scale height can vary significantly depending on the assumed thick disc molecular gas fraction. We also find that the molecular gas flares as a function of the radius and follows a tight exponential law with a scale length of (0.48 ± 0.01)r25. We used the density solutions to produce the column density maps and spectral cubes to examine the ideal observing conditions to identify a thick molecular disc in galaxies. We find that unless the molecular disc is an edge-on system and imaged with a high spatial resolution (≲100 pc), it is extremely hard to identify a thick molecular disc in a column density map. The spectral analysis further reveals that at moderate to high inclination (i ≳ 40°), spectral broadening can fictitiously introduce the signatures of a two-component disc into the spectral cube of a single-component disc. Hence, we conclude that a low inclination molecular disc imaged with high spatial resolution would serve as the ideal site for identifying the thick molecular disc in galaxies.

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“…García-Benito et al 2019), or the presence of dark matter mass (e.g. Das et al 2020). The variation of the mass discrepancy could also be explained with an uncounted gas mass in the galaxies, and this is expected to be significant for late-type systems (e.g.…”

Section: Photometric Stellar Kinematic and Dynamical Propertiesmentioning

confidence: 99%

Star formation quenching stages of active and non-active galaxies

Kalinova

Colombo

Sánchez

et al. 2021

A&A

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The mechanisms that bring galaxies to strongly reduce their star formation activity (star-formation quenching) remain poorly understood. To better study galaxy evolution, we propose a classification based on maps of ionised hydrogen distribution traced by the kiloparsec-resolved, equivalent width of Hα maps, and the nuclear activity of the galaxies using information from the Baldwin-Philips-Terlevich diagnostic diagrams. Using these tools, we group a sample of 238 galaxies from the Calar Alto Legacy Integral Field spectroscopy Area survey in six quenching stages (QSs): (i) objects dominated by recent star formation; (ii) systems that present a quiescent-nuclear-ring structure in their centre; (iii) galaxies that are centrally quiescent; (iv) galaxies with no clear pattern in their ionisation gas distribution (mixed); (v) systems that posses only a few star-forming regions (nearly retired), or (vi) galaxies that are completely quiescent (fully retired). Regarding their nuclear activity, we further divide the galaxies into two groups: active systems that host a weak or strong active galactic nucleus (AGN) at their centre, and non-active objects. Galaxies grouped into quenching-stage classes occupy specific locations on the star-formation-rate versus stellar mass diagram. The ‘blue cloud’ is populated by the star-forming and the quiescent-nuclear-ring galaxies, the ‘green valley’ is populated by centrally quiescent and mixed systems, and the ‘red sequence’ by the nearly- and fully retired objects. Generally, galaxies that host a weak or strong AGN show properties comparable to those of their non-active counterparts at the same QSs, except for the AGN-hosting star-forming systems. The degree of star-formation quenching increases along the present emission-line pattern sequence from star-forming to fully retired. The proposed emission-line classes reinforce the ‘inside-out’ quenching scenario, which foresees that the suppression of star formation begins from the central regions of the galaxies.

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

Cited by 32 publications

References 80 publications

Barred spiral galaxies in modified gravity theories

Barred spiral galaxies in modified gravity theories

Theoretical modelling of two-component molecular discs in spiral galaxies

Star formation quenching stages of active and non-active galaxies

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