An Hα survey aiming at the detection of extraplanar diffuse ionized gas in halos of edge–on spiral galaxies^*,**

II. The Hα survey atlas and catalog

¹ Astronomisches Institut, Ruhr–Universität Bochum, 44780 Bochum, Germany e-mail: dettmar@astro.ruhr-uni-bochum.de
² Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA ()

Corresponding author: J. Rossa, jrossa@stsci.edu

Received: 14 February 2003
Accepted: 6 May 2003

Abstract

In this second paper on the investigation of extraplanar diffuse ionized gas in nearby edge–on spiral galaxies we present the actual results of the individual galaxies of our Hα imaging survey. A grand total of 74 galaxies have been studied, including the 9 galaxies of a recently studied sub–sample [CITE]. 40.5% of all studied galaxies reveal extraplanar diffuse ionized gas, whereas in 59.5% of the survey galaxies no extraplanar diffuse ionized gas could be detected. The average distances of this extended emission above the galactic midplane range from 1–2 kpc, while individual filaments in a few galaxies reach distances of up to  kpc. In several cases a pervasive layer of ionized gas was detected, similar to the Reynolds layer in our Milky Way, while other galaxies reveal only extended emission locally. The morphology of the diffuse ionized gas is discussed for each galaxy and is compared with observations of other important ISM constituents in the context of the disk–halo connection, in those cases where published results were available. Furthermore, we present the distribution of extraplanar dust in these galaxies, based on an analysis of the unsharp–masked R–band images. The results are compared with the distribution of the diffuse ionized gas.