Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas | Zendy

Dhanesh Krishnarao | Zendy; Robert A. Benjamin | Zendy; L. M. Haffner | Zendy

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Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas

Author(s) -

Dhanesh Krishnarao,

Robert A. Benjamin,

L. M. Haffner

Publication year - 2020

Publication title -

science advances

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 5.928

H-Index - 146

ISSN - 2375-2548

DOI - 10.1126/sciadv.aay9711

Subject(s) - physics , astrophysics , galaxy , radius , angstrom , astronomy , emission spectrum , line (geometry) , ionization , doubly ionized oxygen , balmer series , extinction (optical mineralogy) , spectral line , optics , chemistry , ion , computer science , crystallography , geometry , computer security , mathematics , quantum mechanics

Optical emission lines are used to categorize galaxies into three groups according to their dominant central radiation source: active galactic nuclei, star formation, or low-ionization (nuclear) emission regions [LI(N)ERs] that may trace ionizing radiation from older stellar populations. Using the Wisconsin H-Alpha Mapper, we detect optical line emission in low-extinction windows within eight degrees of Galactic Center. The emission is associated with the 1.5-kiloparsec-radius "Tilted Disk" of neutral gas. We modify a model of this disk and find that the hydrogen gas observed is at least 48% ionized. The ratio [NII] λ6584 angstroms/Hα λ6563 angstroms increases from 0.3 to 2.5 with Galactocentric radius; [OIII] λ5007 angstroms and Hβ λ4861 angstroms are also sometimes detected. The line ratios for most Tilted Disk sightlines are characteristic of LI(N)ER galaxies.

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