Journal
ASTROPHYSICAL JOURNAL
Volume 647, Issue 2, Pages 1018-1029Publisher
IOP PUBLISHING LTD
DOI: 10.1086/505464
Keywords
galaxies : halos; galaxies : individual (NGC 891); galaxies : kinematics and dynamics
Categories
Ask authors/readers for more resources
We present high and moderate spectral resolution spectroscopy of diffuse ionized gas ( DIG) emission in the halo of NGC 891. The data were obtained with the SparsePak integral field unit at the WIYN Observatory. The wavelength coverage includes the [N II] lambda lambda 6548, 6583, H alpha, and [S II] lambda lambda 6716, 6731 emission lines. Position-velocity (PV) diagrams, constructed using spectra extracted from four SparsePak pointings in the halo, are used to examine the kinematics of the DIG. Using two independent methods, a vertical gradient in azimuthal velocity is found to be present in the northeast quadrant of the halo, with magnitude approximately 15-18 km s(-1) kpc(-1), in agreement with results from H I observations. The kinematics of the DIG suggests that this gradient begins at approximately 1 kpc above the midplane. In another part of the halo, the southeast quadrant, the kinematics is markedly different and suggest rotation at about 175 km s(-1), much slower than the disk but with no vertical gradient. We use an entirely ballistic model of disk-halo flow in an attempt to reproduce the kinematics observed in the northeast quadrant. Analysis shows that the velocity gradient predicted by the ballistic model is far too shallow. Based on intensity cuts made parallel to the major axis in the ballistic model and an H alpha image of NGC 891 from the literature, we conclude that the DIG halo is much more centrally concentrated than the model, suggesting that hydrodynamics dominate over ballistic motion in shaping the density structure of the halo. Velocity dispersion measurements along the minor axis of NGC 891 seem to indicate a lack of radial motions in the halo, but the uncertainties do not allow us to set firm limits.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available