H I Velocity Dispersion in NGC 1058

We present excellent-resolution and high-sensitivity Very Large Array observations of the 21 cm H I line emission from the face-on galaxy NGC 1058, providing the first reliable study of the H I profile shapes throughout the entire disk of an external galaxy. Our observations show an intriguing picture of the interstellar medium; throughout this galaxy velocity dispersions range between 4 and 15 km s-1 but are not correlated with star formation, stars, or the gaseous spiral arms. The velocity dispersions decrease with radius, but this global trend has a large scatter as there are several isolated, resolved regions of high dispersion. The decline of starlight with radius is much steeper than that of the velocity dispersions or that of the energy in the gas motions.

[1]  Juntai Shen,et al.  Galactic warps induced by cosmic infall , 2006, astro-ph/0604529.

[2]  R. Klessen,et al.  Control of Star Formation in Galaxies by Gravitational Instability , 2004, astro-ph/0407247.

[3]  G. Rüdiger,et al.  Interstellar turbulence driven by the magnetorotational instability , 2004 .

[4]  E. Ostriker,et al.  Thermal and Magnetorotational Instability in the Interstellar Medium: Two-dimensional Numerical Simulations , 2003, astro-ph/0310510.

[5]  R. Klessen,et al.  Control of star formation by supersonic turbulence , 2000, astro-ph/0301093.

[6]  J. Sellwood,et al.  Differential Rotation and Turbulence in Extended H I Disks , 1998, astro-ph/9806307.

[7]  M. Rupen.  Spectral Line Observing II: Calibration and Analysis , 1999 .

[8]  R. Wyse,et al.  Discovery of Recent Star Formation in the Extreme Outer Regions of Disk Galaxies , 1998, astro-ph/9808151.

[9]  R. Wyse,et al.  The Extreme Outer Regions of Disk Galaxies. I. Chemical Abundances of H II Regions , 1998, astro-ph/9805166.

[10]  L. Young,et al.  The Neutral Interstellar Medium in Nearby Dwarf Galaxies. III. Sagittarius DIG, LGS 3, and Phoenix , 1997 .

[11]  R. Braun.  The Temperature and Opacity of Atomic Hydrogen in Spiral Galaxies , 1997, astro-ph/9702111.

[12]  L. Young,et al.  The Neutral Interstellar Medium in Nearby Dwarf Galaxies. II. NGC 185, NGC 205, and NGC 147 , 1997 .

[13]  R. Olling.  NGC 4244: A Low Mass Galaxy With a Falling Rotation Curve and a Flaring Gas Layer , 1996, astro-ph/9605110.

[14]  L. Young,et al.  The Neutral Interstellar Medium in Nearby Dwarf Galaxies. I. Leo A , 1996 .

[15]  S. Malhotra,et al.  The Vertical Distribution and Kinematics of H i and Mass Models of the Galactic Disk , 1994, astro-ph/9411088.

[16]  S. Malhotra,et al.  The Vertical Equilibrium of Molecular Gas in the Galactic Disk , 1994, astro-ph/9404028.

[17]  M. Merrifield.  The kinematics of face-on disc galaxies, and the nature of the Galactic H I layer , 1993 .

[18]  R. Walterbos,et al.  Physical properties of neutral gas in M31 and the Galaxy , 1992 .

[19]  C. Gehman,et al.  Vertical distribution and support of galactic H I , 1991 .

[20]  G. Helou,et al.  NGC 1058 - Gas motions in an extended, quiescent spiral disk , 1990 .

[21]  S. Kulkarni,et al.  Neutral Hydrogen and the Diffuse Interstellar Medium , 1988 .

[22]  B. Lewis.  H I survey of face-on galaxies - the frequency of distortions in H I disks , 1987 .

[23]  M. Fich,et al.  The fraction of high velocity dispersion H I in the Galaxy , 1985 .

[24]  B. Lewis.  Face-on galaxies , 1984 .

[25]  F. Lockman,et al.  The H I halo in the inner galaxy , 1984 .

[26]  J. Ostriker,et al.  A theory of the interstellar medium - Three components regulated by supernova explosions in an inhomogeneous substrate , 1977 .

[27]  B. Lewis.  The redshifts of compact nuclei , 1975 .

[28]  Kenneth I. Kellermann,et al.  Galactic and Extragalactic Radio Astronomy , 1974 .