Kinematics and mass modelling of M33: Hα observations

Kam, Sié; Carignan, C.; Chemin, L.; Amram, P.; Épinat, B.

doi:10.1093/mnras/stv517

Cited by 50 publications

(77 citation statements)

References 91 publications

(119 reference statements)

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“…As shown in Table 2, the mean column densities for these blueshifted components are N S II = 10 15.17 cm −2 , N P II = 10 13.52 cm −2 , N Fe II = 10 14.26 cm −2 , and N Si IV = 10 13.43 cm −2 , and their mean Doppler widths are b ∼ 25 − 40 km s −1 . We find that these blueshifted components could be due to the expansion of local H II regions into M33's ISM, since both their b values and measured velocities are consistent with the large velocity dispersions found in the ionized gas of H II regions (σ ∼ 20 − 30 km s −1 ; Kam et al 2015) and in the H I 21-cm emission across the M33 disk (σ ∼ 18.5 km s −1 ; Putman et al 2009). In particular, the giant H II region NGC 604 (i.e., S5) has been found to be undergoing multiple blowouts (Tenorio-Tagle et al 2000), consistent with the blue-shifted components we detect for S5.…”

Section: Tentative Detection Of Slow Windssupporting

confidence: 80%

HST/Cos Observations of Ionized Gas Accretion at the Disk–halo Interface of M33

Zheng

Peek

Werk

et al. 2017

ApJ

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We report the detection of accreting ionized gas at the disk-halo interface of the nearby galaxy M33. We analyze HST/COS absorption-line spectra of seven ultraviolet-bright stars evenly distributed across the disk of M33. We find Si IV absorption components consistently redshifted relative to the bulk M33's ISM absorption along all the sightlines. The Si IV detection indicates an enriched, diskwide, ionized gas inflow toward the disk. This inflow is most likely multi-phase as the redshifted components can also be observed in ions with lower ionization states (e.g., S II, P II, Fe II, Si II). Kinematic modeling of the inflow is consistent with an accreting layer at the disk-halo interface of M33, which has an accretion velocity of 110 +15 −20 km s −1 at a distance of 1.5+1.0 −1.0 kiloparsec above the disk. The modeling indicates a total mass of ∼ 3.9 × 10 7 M for the accreting material at the diskhalo interface on the near side of the M33 disk , with an accretion rate of ∼ 2.9 M yr −1 . The high accretion rate and the level of metal-enrichment suggest the inflow is likely to be the fall back of M33 gas from a galactic fountain and/or the gas pulled loosed during a close interaction between M31 and M33. Our study of M33 is the first to unambiguously reveal the existence of a disk-wide, ionized gas inflow beyond the Milky Way, providing a better understanding of gas accretion in the vicinity of a galaxy disk.

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Section: Tentative Detection Of Slow Windssupporting

confidence: 80%

HST/Cos Observations of Ionized Gas Accretion at the Disk–halo Interface of M33

Zheng

Peek

Werk

et al. 2017

ApJ

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“…The Hα velocity dispersion profile, corrected from instrumental broadening, is shown in Fig. 3 and listed in Appendix C. The mean dispersion is 20 km s −1 for a standard deviation of ∼2 km s −1 , which is comparable to values found for many other star-forming galaxies of similar morphology and mass (Epinat et al 2010;Kam et al 2015). The profile variations of the density and dispersion remain too small to imply a significant gas asymmetric drift.…”

Section: Tangential and Radial Velocities In M 99supporting

confidence: 58%

Asymmetric mass models of disk galaxies

Chemin

Huré

Soubiran

et al. 2016

A&A

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Mass models of galactic disks traditionally rely on axisymmetric density and rotation curves, paradoxically acting as if their most remarkable asymmetric features, such as lopsidedness or spiral arms, were not important. In this article, we relax the axisymmetry approximation and introduce a methodology that derives 3D gravitational potentials of disk-like objects and robustly estimates the impacts of asymmetries on circular velocities in the disk midplane. Mass distribution models can then be directly fitted to asymmetric line-of-sight velocity fields. Applied to the grand-design spiral M 99, the new strategy shows that circular velocities are highly nonuniform, particularly in the inner disk of the galaxy, as a natural response to the perturbed gravitational potential of luminous matter. A cuspy inner density profile of dark matter is found in M 99, in the usual case where luminous and dark matter share the same center. The impact of the velocity nonuniformity is to make the inner profile less steep, although the density remains cuspy. On another hand, a model where the halo is core dominated and shifted by 2.2−2.5 kpc from the luminous mass center is more appropriate to explain most of the kinematical lopsidedness evidenced in the velocity field of M 99. However, the gravitational potential of luminous baryons is not asymmetric enough to explain the kinematical lopsidedness of the innermost regions, irrespective of the density shape of dark matter. This discrepancy points out the necessity of an additional dynamical process in these regions: possibly a lopsided distribution of dark matter.

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“…Minimizing the dark matter component during fitting is needed to provide amounts of baryonic matter compatible with luminosity, e.g., [5,16,17,20]. The arbitrariness of this procedure proves that the density summation is problematic from a mathematical and physical viewpoint.…”

Section: Limitations In Applying Poisson's Equationmentioning

confidence: 99%

Implications of Geometry and the Theorem of Gauss on Newtonian Gravitational Systems and a Caveat Regarding Poisson’s Equation

Hofmeister

Criss

2017

Galaxies

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Galactic mass consistent with luminous mass is obtained by fitting rotation curves (RC = tangential velocities vs. equatorial radius r) using Newtonian force models, or can be unambiguously calculated from RC data using a model based on spin. In contrast, mass exceeding luminous mass is obtained from multi-parameter fits using potentials associated with test particles orbiting in a disk around a central mass. To understand this disparity, we explore the premises of these mainstream disk potential models utilizing the theorem of Gauss, thermodynamic concepts of Gibbs, the findings of Newton and Maclaurin, and well-established techniques and results from analytical mathematics. Mainstream models assume that galactic density in the axial (z) and r directions varies independently: we show that this is untrue for self-gravitating objects. Mathematics and thermodynamic principles each show that modifying Poisson's equation by summing densities is in error. Neither do mainstream models differentiate between interior and exterior potentials, which is required by potential theory and has been recognized in seminal astronomical literature. The theorem of Gauss shows that: (1) density in Poisson's equation must be averaged over the interior volume; (2) logarithmic gravitational potentials implicitly assume that mass forms a long, line source along the z axis, unlike any astronomical object; and (3) gravitational stability for three-dimensional shapes is limited to oblate spheroids or extremely tall cylinders, whereas other shapes are prone to collapse. Our findings suggest a mechanism for the formation of the flattened Solar System and of spiral galaxies from gas clouds. The theorem of Gauss offers many advantages over Poisson's equation in analyzing astronomical problems because mass, not density, is the key parameter.

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Kinematics and mass modelling of M33: Hα observations

Cited by 50 publications

References 91 publications

HST/Cos Observations of Ionized Gas Accretion at the Disk–halo Interface of M33

HST/Cos Observations of Ionized Gas Accretion at the Disk–halo Interface of M33

Asymmetric mass models of disk galaxies

Implications of Geometry and the Theorem of Gauss on Newtonian Gravitational Systems and a Caveat Regarding Poisson’s Equation

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