Balmer Decrement and IRX Break in Tracing Dust Attenuation at Scales of Individual Star-forming Regions in NGC 628

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Main Authors: Qiao, Man, Liu, Mingfeng, Lyu, Zongfei, Liu, Shuang, Yang, Chao, Shi, Dong Dong, An, Fangxia, Pan, Zhizheng, Liu, Wenhao, Liu, Binyang, Wen, Run, Zhang, Yu Heng, Zheng, Xian Zhong
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Published: 2025
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author Qiao, Man
Liu, Mingfeng
Lyu, Zongfei
Liu, Shuang
Yang, Chao
Shi, Dong Dong
An, Fangxia
Pan, Zhizheng
Liu, Wenhao
Liu, Binyang
Wen, Run
Zhang, Yu Heng
Zheng, Xian Zhong
author_facet Qiao, Man
Liu, Mingfeng
Lyu, Zongfei
Liu, Shuang
Yang, Chao
Shi, Dong Dong
An, Fangxia
Pan, Zhizheng
Liu, Wenhao
Liu, Binyang
Wen, Run
Zhang, Yu Heng
Zheng, Xian Zhong
contents We investigate the relationships between infrared excess (IRX=$L_{\rm IR}/L_{\rm UV}$) and Balmer decrement (${\rm H}α/{\rm H}β$) as indicators of dust attenuation for 609 ${\rm {H\,{\small II}}}$ regions at scales of $\sim 50-200$ pc in NGC 628, utilizing data from AstroSat, James Webb Space Telescope (JWST) and Multi Unit Spectroscopic Explorer (MUSE). Our findings indicate that about three fifths of the sample ${\rm {H\,{\small II}}}$ regions reside within the regime occupied by local star-forming galaxies (SFGs) along the dust attenuation correlation described by their corresponding color excess parameters $E(B-V)_{\rm IRX} = 0.51\,E(B-V)_{{\rm H}α/{\rm H}β}$. Nearly 27$\%$ of the sample exhibits $E(B-V)_{\rm IRX}> E(B-V)_{{\rm H}α/{\rm H}β}$, while a small fraction ($\sim 13\%$) displays significantly lower $E(B-V)_{\rm IRX}$ compared to $E(B-V)_{{\rm H}α/{\rm H}β}$. These results suggest that the correlation between the two dust attenuation indicators no longer holds for spatially resolved ${\rm {H\,{\small II}}}$ regions. Furthermore, the ratio of $E(B-V)_{\rm IRX}$ to $E(B-V)_{{\rm H}α/{\rm H}β}$ remains unaffected by various physical parameters of the ${\rm {H\,{\small II}}}$ regions, including star formation rate (SFR), SFR surface density, infrared luminosity ($L_{\rm IR}$), $L_{\rm IR}$ surface density, stellar mass, gas-phase metallicity, circularized radius, and the distance to galactic center. We argue that the ratio is primarily influenced by the evolution of surrounding interstellar medium (ISM) of the star-forming regions, transitioning from an early dense and thick phase to the late blown-away stage.
format Preprint
id arxiv_https___arxiv_org_abs_2506_21026
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Balmer Decrement and IRX Break in Tracing Dust Attenuation at Scales of Individual Star-forming Regions in NGC 628
Qiao, Man
Liu, Mingfeng
Lyu, Zongfei
Liu, Shuang
Yang, Chao
Shi, Dong Dong
An, Fangxia
Pan, Zhizheng
Liu, Wenhao
Liu, Binyang
Wen, Run
Zhang, Yu Heng
Zheng, Xian Zhong
Astrophysics of Galaxies
We investigate the relationships between infrared excess (IRX=$L_{\rm IR}/L_{\rm UV}$) and Balmer decrement (${\rm H}α/{\rm H}β$) as indicators of dust attenuation for 609 ${\rm {H\,{\small II}}}$ regions at scales of $\sim 50-200$ pc in NGC 628, utilizing data from AstroSat, James Webb Space Telescope (JWST) and Multi Unit Spectroscopic Explorer (MUSE). Our findings indicate that about three fifths of the sample ${\rm {H\,{\small II}}}$ regions reside within the regime occupied by local star-forming galaxies (SFGs) along the dust attenuation correlation described by their corresponding color excess parameters $E(B-V)_{\rm IRX} = 0.51\,E(B-V)_{{\rm H}α/{\rm H}β}$. Nearly 27$\%$ of the sample exhibits $E(B-V)_{\rm IRX}> E(B-V)_{{\rm H}α/{\rm H}β}$, while a small fraction ($\sim 13\%$) displays significantly lower $E(B-V)_{\rm IRX}$ compared to $E(B-V)_{{\rm H}α/{\rm H}β}$. These results suggest that the correlation between the two dust attenuation indicators no longer holds for spatially resolved ${\rm {H\,{\small II}}}$ regions. Furthermore, the ratio of $E(B-V)_{\rm IRX}$ to $E(B-V)_{{\rm H}α/{\rm H}β}$ remains unaffected by various physical parameters of the ${\rm {H\,{\small II}}}$ regions, including star formation rate (SFR), SFR surface density, infrared luminosity ($L_{\rm IR}$), $L_{\rm IR}$ surface density, stellar mass, gas-phase metallicity, circularized radius, and the distance to galactic center. We argue that the ratio is primarily influenced by the evolution of surrounding interstellar medium (ISM) of the star-forming regions, transitioning from an early dense and thick phase to the late blown-away stage.
title Balmer Decrement and IRX Break in Tracing Dust Attenuation at Scales of Individual Star-forming Regions in NGC 628
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2506.21026