Diffuse Ionized Gas in CALIFA (and MaNGA) galaxies

We use spatially resolved spectroscopy from the CALIFA survey to study the nature of the line emitting gas in galaxies of different Hubble types, focusing on the separation of star-forming (SF) regions from those better characterized as diffuse ionized gas (DIG). The diagnosis is carried out in terms of the equivalent width of Ha (W_Ha). Three nebular regimes are identified: (1) Regions where W_Ha < 3 A define what we call the hDIG, the component of the DIG where photoionization is dominated by hot, low mass, evolved stars (HOLMES). (2) Regions where W_Ha > 14 A trace SF complexes. (3) W_Ha values in the intermediate 3--14 A range reflect a mixed regime (mDIG) where more than one process contributes. This three-tier scheme is inspired both by theoretical and empirical considerations. Its application to CALIFA galaxies of different types and inclinations leads to the following results: (i) The hDIG component is prevalent throughout ellipticals and S0's as well as in bulges, and explains the strongly bimodal distribution of W_Ha both among and within galaxies. (ii) Early type spirals have some hDIG in their disks, but this component becomes progressively less relevant for  later Hubble types. (iii) hDIG emission is also present above and below galactic disks, as  seen in several edge-on spirals in our sample. (iv) The SF/mDIG proportion grows steadily from early to late types spirals, and from inner to outer radii. (v) Besides circumventing basic inconsistencies in conventional DIG/SF separation criteria based on the Ha surface brightness, our W_Ha-based method produces results in agreement with a classical diagnostic-diagram analysis.

This same overall methodology was recently applied to over 2000 galaxies from the MaNGA survey. Preliminary results of  this analysis will also presented.

25/01/2018 - 12:30
Dr. Roberto Cid Fernandes
Universidade Federal de Santa Catarina, Brazil