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

By R. Boomsma, T. Oosterloo, Filippo Fraternali, J. Hulst, R. Sancisi. 2008

155 citations recorded by the source corpus.

We present a study of the distribution and kinematics of the neutral gas in the low-inclination Scd galaxy NGC 6946. The galaxy has been observed for 192 h at 21-cm with the Westerbork Synthesis Radio Telescope. These are among the deepest observations ever obtained for a nearby galaxy. We detect widespread high-velocity HI (up to about 100 km s(-1)) and find 121 HI holes, most of which are located in the inner regions where the gas density and the star formation rate are higher. Much of the high-velocity gas appears to be related to star formation and to be, in some cases, associated with HI holes. The overall kinematics of the high-velocity gas is characterized by a slower rotation as compared with the regular disk rotation. We conclude that the high-velocity gas in NGC 6946 is extra-planar and has the same properties as the gaseous halos observed in other spiral galaxies including the Milky Way. Stellar feedback (galactic fountain) is probably at the origin of most of the high-velocity gas and of the HI holes. There are also indications, especially in the outer regions, -an extended HI plume, velocity anomalies, sharp edges, and large-scale asymmmetries-pointing to tidal encounters and recent gas accretion.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/65c156755f5cb946359da9d62b61c45b23bca47e

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In Astronomy and Astrophysics

1. M. Cappellari
2. T. Naab
3. M. Sarzi
4. P. Hopkins
5. Roger Davies
6. Eric Emsellem
7. M. Bureau
8. L. Hernquist

In Instrumentation

1. M. Cappellari
2. T. Naab
3. M. Sarzi
4. M. Bureau
5. Eric Emsellem
6. D. Krajnovi'c
7. Roger Davies
8. P. de Zeeuw

Citations in the corpus

• The current status of galaxy formation (2012, background): “Other spiral galaxies show extensive reservoirs of HI in their outer regions, for example NGC 6946 (Boomsma et al., 2008) and UGC 2082 (Heald et al., 4 Joseph Silk1,2,3, Gary A. Mamon1 2011).”
• Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions (2011, unknown): “Velocity data for NGC 6946 include both HI data that define the outer, flat portion of the rotation curve [66] and Hα data from two independent observations [54, 114] that define the shape of the inner rotation curve.”
• The ATLAS3D project - XIII. Mass and morphology of H I in early-type galaxies as a function of environment (2011, methodology): “We verify the prediction of this fit at low column density by analysing a very deep WSRT H I image of a prototypical nearly face-on spiral galaxy, NGC 6946 (Boomsma et al. 2008).”
• FORMING REALISTIC LATE-TYPE SPIRALS IN A ΛCDM UNIVERSE: THE ERIS SIMULATION (2011, background): “These holes are mostly located within the bright optical disk and preferentially in regions of high star formation: they are kpc in size, as observed, e.g., in the nearby low-inclination spiral galaxy NGC 6946 (Boomsma et al. 2008).”
• The mass function of young star clusters in spiral galaxies (2008, background): “The gas resides in a large, orderly rotating disc (Boomsma et al. 2008) with no major distortions apart from a number of (probably extra-planar) high velocity clouds.”