HI holes and high-velocity clouds in the spiral galaxy NGC 6946

Boomsma, Rense; Oosterloo, Tom; Fraternali, Filippo; Hulst, J. M. van der; Sancisi, R.

doi:10.1051/0004-6361:200810120

Cited by 197 publications

(292 citation statements)

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“…The vertical rotational gradient estimated in Sect. 3.3 is the same as the one found by Oosterloo et al (2007) for NGC 891; inward radial motions of 10−20 km s −1 have been found by Fraternali et al (2002) in the H i halo of NGC 2403; Boomsma et al (2008) showed the presence of vertical motions for halo gas clouds in NGC 6946.…”

Section: Comparison With External Galaxiessupporting

confidence: 80%

Modelling the H i halo of the Milky Way

Marasco

Fraternali

2010

A&A

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Aims. We studied the global distribution and kinematics of the extra-planar neutral gas in the Milky Way.Methods. We built 3D models for a series of Galactic H i layers, projected them for an inside view, and compared them with the Leiden-Argentina-Bonn 21-cm observations. Results. We show that the Milky Way disk is surrounded by an extended halo of neutral gas with a vertical scale-height of 1.6 +0.6 −0.4 kpc and an H i mass of 3.2 +1.0 −0.9 × 10 8 M , which is ∼5−10% of the total Galactic H i. This H i halo rotates more slowly than the disk with a vertical velocity gradient of −15 ± 4 km s −1 kpc −1 . We found evidence for a global infall motion in the halo, both vertical (20 +5 −7 km s −1 ) and radial (30 +7 −5 km s −1 ). Conclusions.The Milky Way H i extra-planar layer shows properties similar to the halos of external galaxies, which is compatible with it being predominantly produced by supernova explosions in the disk. It is most likely composed of distinct gas complexes with masses of ∼10 4−5 M , of which the intermediate velocity clouds are the local manifestations. The classical high-velocity clouds appear to be a separate population.

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Section: Comparison With External Galaxiessupporting

confidence: 80%

Modelling the H i halo of the Milky Way

Marasco

Fraternali

2010

A&A

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“…Low-inclination galaxies that show prominent beards are e.g. NGC 2403 (Fraternali et al 2002) and NGC 6946 (Boomsma et al 2008). Position-velocity slices along the major axis of NGC 1167 (Fig.…”

Section: Identifying Halo Gasmentioning

confidence: 99%

Cold gas in massive early-type galaxies: the case of NGC 1167

Struve

Oosterloo

Sancisi

et al. 2010

A&A

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We present a study of the morphology and kinematics of the neutral hydrogen in the gas-rich (M HI = 1.5 × 10 10 M ), massive earlytype galaxy NGC 1167, which was observed with the Westerbork Synthesis Radio Telescope (WSRT). The H i is located in a 160 kpc disk (≈3 × D 25 ) and has low surface density (≤2 M pc −2 ). The disk shows regular rotation for r < 65 kpc but several signs of recent and ongoing interaction and merging with fairly massive companions are observed. No population of cold gas clouds is observed -in contrast to what is found in some spiral galaxies. This suggests that currently the main mechanism bringing in cold gas to the disk is the accretion of fairly massive satellite galaxies, rather than the accretion of a large number of small gas clumps. NGC 1167 is located in a (gas-) rich environment: we detect eight companions with a total H i mass of ∼6 × 10 9 M within a projected distance of 350 kpc. Deep optical images show a disrupted satellite at the northern edge of the H i disk. The observed rotation curve shows a prominent bump of about 50 km s −1 (in the plane of the disk) at r ≈ 1.3 × R 25 . This feature in the rotation curve occurs at the radius where the H i surface density drops significantly and may be due to large-scale streaming motions in the disk. We suspect that both the streaming motions and the H i density distribution are the result of the interaction/accretion with the disrupted satellite. Like in other galaxies with wiggles and bumps in the rotation curve, H i scaling describes the observed rotation curve best. We suggest that interactions create streaming motions and features in the H i density distribution and that this is the reason for the success of H i scaling in fitting such rotation curves.

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“…Observationally, in moderately inclined galaxies the very existence of the lag allows the disentangling of extraplanar gas from gas that resides in the plane, e.g. in NGC 2403 (Fraternali et al 2002), NGC 4559 (Barbieri et al 2005), and NGC 6946 (Boomsma et al 2008).…”

Section: Introductionmentioning

confidence: 99%

HALOGAS: Extraplanar gas in NGC 3198

Gentile

Józsa

Serra

et al. 2013

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We present the analysis of new, deep H observations of the spiral galaxy NGC 3198 as part of the Westerbork Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey, with the main aim of investigating the presence, amount, morphology, and kinematics of extraplanar gas. We present models of the H observations of NGC 3198. The model that matches best the observed data cube features a thick disk with a scale height of ∼3 kpc and an H mass of about 15% of the total H mass; this thick disk also has a decrease in rotation velocity as a function of height (lag) of 7-15 km s −1 kpc −1 (though with large uncertainties). This extraplanar gas is detected for the first time in NGC 3198. Radially, this gas appears to extend slightly beyond the actively star-forming body of the galaxy (as traced by the Hα emission), but it is not more radially extended than the outer, fainter parts of the stellar disk. Compared to previous studies, thanks to the improved sensitivity we trace the rotation curve out to larger radii. We model the rotation curve in the framework of modified Newtonian dynamics (MOND) and confirm that, with the allowed distance range we assumed, fit quality is modest in this galaxy, but the new outer parts are explained in a satisfactory way.

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HI holes and high-velocity clouds in the spiral galaxy NGC 6946

Cited by 197 publications

References 50 publications

Modelling the H i halo of the Milky Way

Modelling the H i halo of the Milky Way

Cold gas in massive early-type galaxies: the case of NGC 1167

HALOGAS: Extraplanar gas in NGC 3198

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