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

¹ Max-Planck Institute for Astrophysics, Karl-Schwarzschild-Str 1, 85748 Garching, Germany
e-mail: ajones@mpa-garching.mpg.de
² Apache Point Observatory, PO Box 59, Sunspot, NM 88349, USA
³ Special Astrophysical Observatory of the Russian AS, 369167 Nizhnij Arkhyz, Russia
⁴ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁵ Department of Astronomy, University of Wisconsin-Madison, 475N. Charter St., Madison WI 53703, USA
⁶ PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
⁷ Department of Physics and Astronomy, University of Utah, 115 S. 1400 E., Salt Lake City, UT 84112, USA
⁸ UCO/Lick Observatory, University of California, 1156 High St. Santa Cruz, Santa Cruz, CA 95064, USA
⁹ Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
¹⁰ Department of Physics and Astronomy, Bates College, Lewiston, ME 04240, USA
¹¹ McDonald Observatory, The University of Texas at Austin, 1 University Station, Austin, TX 78712, USA
¹² Departamento de Física, CCNE, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil
¹³ Laboratório Interinstitucional de e-Astronomia-LInea, Rua Gal. José Cristino 77, 20921-400 Rio de Janeiro, Brazil
¹⁴ Instituto de Astronomia, Universidad Nacional Autónoma de México, A.P. 70-264, 04510 Mexico, D.F., Mexico
¹⁵ Institute of Cosmology & Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX, UK
¹⁶ School of Physical Sciences, The Open University, Milton Keynes, MK1 15, UK
¹⁷ Department of Physics and Astronomy, University of Kentucky, 505 Rose Street, Lexington, KY 40506, USA

Received: 28 September 2016
Accepted: 8 December 2016

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 Hα, Hβ, [O ii]λλ3726, 3729, [O iii]λ5007, [N ii]λλ6549, 6584, and [S ii]λλ6717, 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 [O ii] and Hα emission lines are comparable, unlike in the disk where Hα 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 H ii regions compared with low specific star-formation rate galaxies. The less concentrated and lower stellar mass samples exhibit line ratios that are more like H ii 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 [N ii]/Hα and [O ii]/Hα ratios between the disk and the halo.