We continue our empirical study of the emission line flux originating in thecool ($T\sim10^4$ K) gas that populates the halos of galaxies and theirenvironments. Specifically, we present results obtained for a sample of galaxypairs with a range of projected separations, {\bf $10 < {S_p/\rm kpc} < 200$},and mass ratios $<$ 1:5, intersected by 5,443 SDSS lines of sight at projectedradii of 10 to 50 kpc from either or both of the two galaxies. We findsignificant enhancement in H$\alpha$ emission and a moderate enhancement in [N{\small II}]6583 emission for low mass pairs (mean stellar mass per galaxy,$\overline{\rm M}_*, <10^{10.4} {\rm M}_\odot$) relative to the results from acontrol sample. This enhanced H$\alpha$ emission comes almost entirely fromsight lines located between the galaxies, consistent with a short-term,interaction-driven origin for the enhancement. We find no enhancement inH$\alpha$ emission, but significant enhancement in [N {\small II}]6583 emissionfor high mass ($\overline{\rm M}_* >10^{10.4}{\rm M}_\odot$) pairs.Furthermore, we find a dependence of the emission line properties on the galaxypair mass ratio such that those with a mass ratio below 1:2.5 have enhanced [N{\small II}]6583 and those with a mass ratio between 1:2.5 and 1:5 do not. Inall cases, departures from the control sample are only detected for close pairs($S_p <$ 100 kpc). Attributing an elevated [N {\small II}]6583/H$\alpha$ ratioto shocks, we infer that shocks play a role in determining the CGM propertiesfor close pairs that are among the more massive and have mass ratios closer to1:1.

We present a new catalog of HII regions based on the integral fieldspectroscopy (IFS) data of the extended CALIFA and PISCO samples. The selectionof HII regions was based on two assumptions: a clumpy structure with highcontrast of H$\alpha$ emission and an underlying stellar population comprisingyoung stars. The catalog provides the spectroscopic information of 26,408individual regions corresponding to 924 galaxies, including the fluxintensities and equivalent widths of 51 emission lines covering the wavelengthrange between 3745-7200A. To our knowledge, this is the largest catalog ofspectroscopic properties of HII regions. We explore a new approach todecontaminate the emission lines from diffuse ionized gas contribution. Thisdiffuse gas correction was estimated to correct every emission line within theconsidered spectral range. With the catalog of HII regions corrected, newdemarcation lines are proposed for the classical diagnostic diagrams. Finally,we study the properties of the underlying stellar populations of the HIIregions. It was found that there is a direct relationship between theionization conditions on the nebulae and the properties of stellar populationsbesides the physicals condition on the ionized regions.