# Interpreting the star formation - extinction relation with MaNGA

Huan Li, Stijn Wuyts, Lei Hao, Lin Lin, Man I Lam, Médéric Boquien, Brett H. Andrews, Donald P. Schneider

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### Abstract

We investigate the resolved relation between local extinction and star formation surface density within nearby star-forming galaxies selected from the MaNGA survey. Balmer decrement measurements imply an extinction of the H{\alpha} line emission which scales approximately linearly with the logarithm of the star formation surface density: $A_{H{\alpha}} = 0.46 \log(\Sigma_{SFR}) + 1.53$. Secondary dependencies are observed such that, at a given $\Sigma_{SFR}$, regions of lower metallicity and/or enhanced H{\alpha} equivalent width (EW) suffer less obscuration than regions of higher metallicity and/or lower H{\alpha} EW. Spaxels lying above the mean relation also tend to belong to galaxies that are more massive, larger and viewed under higher inclination than average. We present a simple model in which the observed trends can be accounted for by a metallicity-dependent scaling between $\Sigma_{SFR}$ and $\Sigma_{dust}$ via a super-linear Kennicutt-Schmidt relation ($n_{KS} \sim 1.47$) and a dust-to-gas ratio which scales linearly with metallicity (DGR($Z_{\odot}$) = 0.01). The relation between the resulting total dust column and observed effective extinction towards nebular regions requires a geometry for the relative distribution of H{\alpha} emitting regions and dust that deviates from a uniform foreground screen and also from an entirely homogeneous mixture of dust and emitting sources. The best-fit model features an H{\alpha} EW and galactocentric distance dependent fraction of the dust mass in a clumpy foreground screen in front of a homogeneous mixture.
Original language English 63 15 Astrophysical Journal 872 1 https://doi.org/10.3847/1538-4357/aafb6e Published - 11 Feb 2019

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### Cite this

Li, H., Wuyts, S., Hao, L., Lin, L., Lam, M. I., Boquien, M., ... Schneider, D. P. (2019). Interpreting the star formation - extinction relation with MaNGA. Astrophysical Journal, 872(1), [63]. https://doi.org/10.3847/1538-4357/aafb6e

Interpreting the star formation - extinction relation with MaNGA. / Li, Huan; Wuyts, Stijn; Hao, Lei; Lin, Lin; Lam, Man I; Boquien, Médéric; Andrews, Brett H.; Schneider, Donald P.

In: Astrophysical Journal, Vol. 872, No. 1, 63, 11.02.2019.

Research output: Contribution to journalArticle

Li, H, Wuyts, S, Hao, L, Lin, L, Lam, MI, Boquien, M, Andrews, BH & Schneider, DP 2019, 'Interpreting the star formation - extinction relation with MaNGA', Astrophysical Journal, vol. 872, no. 1, 63. https://doi.org/10.3847/1538-4357/aafb6e
Li, Huan ; Wuyts, Stijn ; Hao, Lei ; Lin, Lin ; Lam, Man I ; Boquien, Médéric ; Andrews, Brett H. ; Schneider, Donald P. / Interpreting the star formation - extinction relation with MaNGA. In: Astrophysical Journal. 2019 ; Vol. 872, No. 1.
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title = "Interpreting the star formation - extinction relation with MaNGA",
abstract = "We investigate the resolved relation between local extinction and star formation surface density within nearby star-forming galaxies selected from the MaNGA survey. Balmer decrement measurements imply an extinction of the H{\alpha} line emission which scales approximately linearly with the logarithm of the star formation surface density: $A_{H{\alpha}} = 0.46 \log(\Sigma_{SFR}) + 1.53$. Secondary dependencies are observed such that, at a given $\Sigma_{SFR}$, regions of lower metallicity and/or enhanced H{\alpha} equivalent width (EW) suffer less obscuration than regions of higher metallicity and/or lower H{\alpha} EW. Spaxels lying above the mean relation also tend to belong to galaxies that are more massive, larger and viewed under higher inclination than average. We present a simple model in which the observed trends can be accounted for by a metallicity-dependent scaling between $\Sigma_{SFR}$ and $\Sigma_{dust}$ via a super-linear Kennicutt-Schmidt relation ($n_{KS} \sim 1.47$) and a dust-to-gas ratio which scales linearly with metallicity (DGR($Z_{\odot}$) = 0.01). The relation between the resulting total dust column and observed effective extinction towards nebular regions requires a geometry for the relative distribution of H{\alpha} emitting regions and dust that deviates from a uniform foreground screen and also from an entirely homogeneous mixture of dust and emitting sources. The best-fit model features an H{\alpha} EW and galactocentric distance dependent fraction of the dust mass in a clumpy foreground screen in front of a homogeneous mixture.",
keywords = "astro-ph.GA",
author = "Huan Li and Stijn Wuyts and Lei Hao and Lin Lin and Lam, {Man I} and M{\'e}d{\'e}ric Boquien and Andrews, {Brett H.} and Schneider, {Donald P.}",
note = "Accepted for publication in ApJ. Figures 2 and 3 show the observed star formation - extinction relation. Figures 9 and 10 show our favored model",
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AU - Li, Huan

AU - Wuyts, Stijn

AU - Hao, Lei

AU - Lin, Lin

AU - Lam, Man I

AU - Boquien, Médéric

AU - Andrews, Brett H.

AU - Schneider, Donald P.

N1 - Accepted for publication in ApJ. Figures 2 and 3 show the observed star formation - extinction relation. Figures 9 and 10 show our favored model

PY - 2019/2/11

Y1 - 2019/2/11

N2 - We investigate the resolved relation between local extinction and star formation surface density within nearby star-forming galaxies selected from the MaNGA survey. Balmer decrement measurements imply an extinction of the H{\alpha} line emission which scales approximately linearly with the logarithm of the star formation surface density: $A_{H{\alpha}} = 0.46 \log(\Sigma_{SFR}) + 1.53$. Secondary dependencies are observed such that, at a given $\Sigma_{SFR}$, regions of lower metallicity and/or enhanced H{\alpha} equivalent width (EW) suffer less obscuration than regions of higher metallicity and/or lower H{\alpha} EW. Spaxels lying above the mean relation also tend to belong to galaxies that are more massive, larger and viewed under higher inclination than average. We present a simple model in which the observed trends can be accounted for by a metallicity-dependent scaling between $\Sigma_{SFR}$ and $\Sigma_{dust}$ via a super-linear Kennicutt-Schmidt relation ($n_{KS} \sim 1.47$) and a dust-to-gas ratio which scales linearly with metallicity (DGR($Z_{\odot}$) = 0.01). The relation between the resulting total dust column and observed effective extinction towards nebular regions requires a geometry for the relative distribution of H{\alpha} emitting regions and dust that deviates from a uniform foreground screen and also from an entirely homogeneous mixture of dust and emitting sources. The best-fit model features an H{\alpha} EW and galactocentric distance dependent fraction of the dust mass in a clumpy foreground screen in front of a homogeneous mixture.

AB - We investigate the resolved relation between local extinction and star formation surface density within nearby star-forming galaxies selected from the MaNGA survey. Balmer decrement measurements imply an extinction of the H{\alpha} line emission which scales approximately linearly with the logarithm of the star formation surface density: $A_{H{\alpha}} = 0.46 \log(\Sigma_{SFR}) + 1.53$. Secondary dependencies are observed such that, at a given $\Sigma_{SFR}$, regions of lower metallicity and/or enhanced H{\alpha} equivalent width (EW) suffer less obscuration than regions of higher metallicity and/or lower H{\alpha} EW. Spaxels lying above the mean relation also tend to belong to galaxies that are more massive, larger and viewed under higher inclination than average. We present a simple model in which the observed trends can be accounted for by a metallicity-dependent scaling between $\Sigma_{SFR}$ and $\Sigma_{dust}$ via a super-linear Kennicutt-Schmidt relation ($n_{KS} \sim 1.47$) and a dust-to-gas ratio which scales linearly with metallicity (DGR($Z_{\odot}$) = 0.01). The relation between the resulting total dust column and observed effective extinction towards nebular regions requires a geometry for the relative distribution of H{\alpha} emitting regions and dust that deviates from a uniform foreground screen and also from an entirely homogeneous mixture of dust and emitting sources. The best-fit model features an H{\alpha} EW and galactocentric distance dependent fraction of the dust mass in a clumpy foreground screen in front of a homogeneous mixture.

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