A tale of two DIGs: The relative role of H II 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 H II 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 and T. G. Williams
單位
出版者
著錄名稱、卷期、頁數 Astronomy & Astrophysics 659, p.29
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_US
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 USA
公開徵稿
出版型式 ,電子版,紙本