SDSS IV MaNGA: Deep observations of extra-planar, diffuse ionized gas around late-type galaxies from stacked IFU spectra

TL;DR

This study uses stacked IFU spectra from the MaNGA survey to analyze the properties of extra-planar diffuse ionized gas around late-type galaxies, revealing variations with galaxy characteristics and extending observations up to 9 kpc from the midplane.

Contribution

First detailed analysis of extra-planar ionized gas in late-type galaxies using stacked IFU spectra, revealing how properties vary with galaxy features.

Findings

Emission lines detectable up to 4-9 kpc from midplane.

Surface brightness and line ratios vary with galaxy properties.

Gas in massive galaxies shows higher temperatures and steeper gradients.

Abstract

We have conducted a study of extra-planar diffuse ionized gas using the first year data from the MaNGA IFU survey. We have stacked spectra from 49 edge-on, late-type galaxies as a function of distance from the midplane of the galaxy. With this technique we can detect the bright emission lines Halpha, Hbeta, [OII]3726, 3729, [OIII]5007, [NII]6549, 6584, and [SII]6717, 6731 out to about 4 kpc above the midplane. With 16 galaxies we can extend this analysis out to about 9 kpc, i.e. a distance of ~2R_e, vertically from the midplane. In the halo, the surface brightnesses of the [OII] and Halpha emission lines are comparable, unlike in the disk where Halpha dominates. When we split the sample by specific star formation rate, concentration index, and stellar mass, each subsample's emission line surface brightness profiles and ratios differ, indicating that extra-planar gas properties can vary. The emission line surface brightnesses of the gas around high specific star formation rate galaxies are higher at all distances, and the line ratios are closer to ratios characteristic of HII regions compared with low specific star formation rate galaxies. The less concentrated and lower stellar mass samples exhibit line ratios that are more like HII regions at larger distances than their more concentrated and higher stellar mass counterparts. The largest difference between different subsamples occurs when the galaxies are split by stellar mass. We additionally infer that gas far from the midplane in more massive galaxies has the highest temperatures and steepest radial temperature gradients based on their [NII]/Halpha and [OII]/Halpha ratios between the disk and the halo.