Line Velocity Field Research Articles

Starburst galaxy NGC 7673: a minor merger remnant

We investigate the kinematics of the luminous starburst galaxy NGC 7673 = Mrk 325, a nearby example of a ‘clumpy irregular galaxy’. Images with the WIYN 3.5m telescope reveal outer wisps associated with mergers, and we suggest NGC 7673 is the survivor of a minor merger. DensePak spectroscopy of the Hα kinematics shows that the H II regions are confined to a rotating disk. The Hα emission line velocity field indicates that although there is widespread star formation across the inner disk, it is still rotating smoothly. The Hα emission profiles over the brightest regions of the galaxy have two components: narrow, FWHM ≈ 50kms−1 lines, and broad, FWHMW ≈ 150 km s−1 lines. The width of the narrow lines is likely due to a combination of averaging effects, stellar winds and SNRs, and possibly gravitational motions within the disk. The origin of the broad component, which eclipses the narrow component in flux over much of the galaxy's inner regions, is still unclear. We may be looking at turbulent gas encased in bubbles carved out by massive stars and their descendants, or possibly some localized outflows from the disk.

Emission line velocity field in the central region of M82

Emission line velocity field in the central region of M82

Velocity field and physical conditions in the active lenticular galaxy NGC 3998

A rotating and expanding flattened distribution of gas is suggested by measurements of the emission line velocity field for the line elliptical/lenticular galaxy NGC 3998, using seven long slit spectrograms in five position angles. Expanding material kinetic energy values of 10 to the 53rd to 10 to the 54th ergs, together with the flat spectrum radio source and nucleus X-ray emission, indicate pronounced nuclear activity. Spectrophotometry of the galactic nucleus shows emission line strengths typical of shocks rather than of photoionization, and line ratios indicate a postshock temperature of 60,000 K and a preshock density of 25 particles/cu cm. Both the stars and the ionized gas of the galaxy have central velocity dispersions of 260 km/s. In view of the high rotational velocity of the stars, NGC 3998 is a lenticular rather than elliptical galaxy.

The - Line Velocity Field in M82

The - Line Velocity Field in M82