Systematic biases in determining dust attenuation curves through galaxy SED fitting

Jianbo Qin; Xian Zhong Zheng; Min Fang; Zhizheng Pan; Stijn Wuyts; Yong Shi; Yingjie Peng; Valentino Gonzalez; Fuyan Bian; Jia-Sheng Huang; Qiu-Sheng Gu; Wenhao Liu; Qinghua Tan; Dong Dong Shi; Jian Ren; Yuheng Zhang; Man Qiao; Run Wen; Shuang Liu

doi:10.1093/mnras/stac132

paper

Systematic biases in determining dust attenuation curves through galaxy SED fitting

arXiv:2201.05467 · doi:10.1093/mnras/stac132

Abstract

While the slope of the dust attenuation curve ( $δ$ ) is found to correlate with effective dust attenuation ( $A_{V}$ ) as obtained through spectral energy distribution (SED) fitting, it remains unknown how the fitting degeneracies shape this relation. We examine the degeneracy effects by fitting SEDs of a sample of local star-forming galaxies (SFGs) selected from the Galaxy And Mass Assembly survey, in conjunction with mock galaxy SEDs of known attenuation parameters. A well-designed declining starburst star formation history is adopted to generate model SED templates with intrinsic UV slope ( $β_{0}$ ) spanning over a reasonably wide range. The best-fitting $β_{0}$ for our sample SFGs shows a wide coverage, dramatically differing from the limited range of $β_{0} < - 2.2$ for a starburst of constant star formation. Our results show that strong degeneracies between $β_{0}$ , $δ$ , and $A_{V}$ in the SED fitting induce systematic biases leading to a false $A_{V}$ -- $δ$ correlation. Our simulation tests reveal that this relationship can be well reproduced even when a flat $A_{V}$ -- $δ$ relation is taken to build the input model galaxy SEDs. The variations in best-fitting $δ$ are dominated by the fitting errors. We show that assuming a starburst with constant star formation in SED fitting will result in a steeper attenuation curve, smaller degeneracy errors, and a stronger $A_{V}$ -- $δ$ relation. Our findings confirm that the $A_{V}$ -- $δ$ relation obtained through SED fitting is likely driven by the systematic biases induced by the fitting degeneracies between $β_{0}$ , $δ$ , and $A_{V}$ .

arXiv comment21 pages, 13 figures, accepted for publication in the MNRAS, Comments welcome!

Systematic biases in determining dust attenuation curves through galaxy SED fitting

Abstract

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