A tale of two DIGs: The relative role of HII regions and low-mass hot evolved stars in powering the diffuse ionised gas (DIG) in PHANGS-MUSE galaxies
學年 110
學期 2
出版（發表）日期 2022-03-01
作品名稱 A tale of two DIGs: The relative role of HII regions and low-mass hot evolved stars in powering the diffuse ionised gas (DIG) in PHANGS-MUSE galaxies
作品名稱（其他語言）
著者 F. Belfiore; F. Santoro; B. Groves; E. Schinnerer; K. Kreckel; S. C. O. Glover; R. S. Klessen; E. Emsellem; G. A. Blanc; E. Congiu; A. T. Barnes; M. Boquien; M. Chevance; D. A. Dale; J. M. Diederik Kruijssen; A. K. Leroy; H.-A. Pan; I. Pessa; A. Schruba; T. G. Williams
單位
出版者
著錄名稱、卷期、頁數 Astronomy & Astrophysics 659, A26
摘要 We use integral field spectroscopy from the PHANGS–MUSE survey, which resolves the ionised interstellar medium structure at ∼50 pc resolution in 19 nearby spiral galaxies, to study the origin of the diffuse ionised gas (DIG). We examine the physical conditions of the diffuse gas by first removing morphologically defined H II regions and then binning the low-surface-brightness areas to achieve significant detections of the key nebular lines in the DIG. A simple model for the leakage and propagation of ionising radiation from H II regions is able to reproduce the observed distribution of Hα in the DIG. This model infers a typical mean free path for the ionising radiation of 1.9 kpc for photons propagating within the disc plane. Leaking radiation from H II regions also explains the observed decrease in line ratios of low-ionisation species ([S II]/Hα, [N II]/Hα, and [O I]/Hα) with increasing Hα surface brightness (ΣHα). Emission from hot low-mass evolved stars, however, is required to explain: (1) the enhanced low-ionisation line ratios observed in the central regions of some of the galaxies in our sample; (2) the observed trends of a flat or decreasing [O III]/Hβ with ΣHα; and (3) the offset of some DIG regions from the typical locus of H II regions in the Baldwin–Phillips–Terlevich (BPT) diagram, extending into the area of low-ionisation (nuclear) emission-line regions (LI[N]ERs). Hot low-mass evolved stars make a small contribution to the energy budget of the DIG (2% of the galaxy-integrated Hα emission), but their harder spectra make them fundamental contributors to [O III] emission. The DIG might result from a superposition of two components, an energetically dominant contribution from young stars and a more diffuse background of harder ionising photons from old stars. This unified framework bridges observations of the Milky Way DIG with LI(N)ER-like emission observed in nearby galaxy bulges.
關鍵字 galaxies: ISM;galaxies: star formation;HII regions;ISM: structure;ISM: general;Astrophysics - Astrophysics of Galaxies
語言 en
ISSN 2329-1273; 2329-1265
期刊性質 國外
收錄於 SCI
產學合作
通訊作者
審稿制度 是
國別 FRA
公開徵稿
出版型式 ,電子版,紙本
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機構典藏連結 ( http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/123338 )