We present a detailed analysis of deep far-infrared observations of the nearby edge-on star-forming galaxy NGC 4631 obtained with the Herschel Space Observatory .
Our PACS images at 70 and 160 \micron show a rich complex of filaments and chimney-like features that extends up to a projected distance of 6 kpc above the plane of the galaxy .
The PACS features often match extraplanar H \alpha , radio-continuum , and soft X-ray features observed in this galaxy , pointing to a tight disk-halo connection regulated by star formation .
On the other hand , the morphology of the colder dust component detected on larger scale in the SPIRE 250 , 350 , and 500 \micron data matches the extraplanar H I streams previously reported in NGC 4631 and suggests a tidal origin .
The PACS 70/160 \micron ratios are elevated in the central \sim 3.0 kpc region above the nucleus of this galaxy ( the “ superbubble ” ) .
A pixel-by-pixel analysis shows that dust in this region has a higher temperature and/or an emissivity with a steeper spectral index ( \beta > 2 ) than the dust in the disk , possibly the result of the harsher environment in the superbubble .
Star formation in the disk seems energetically insufficient to lift the material out of the disk , unless it was more active in the past or the dust-to-gas ratio in the superbubble region is higher than the Galactic value .
Some of the dust in the halo may also have been tidally stripped from nearby companions or lifted from the disk by galaxy interactions .