Exploring the Correlation between $\mathrm{H}\hat{\mathrm{I}}\pm$-to-UV Ratio and Burstiness for Typical Star-forming Galaxies at $z\sim 2$

Abstract

The $\mathrm{H}\hat{\mathrm{I}}\pm$-to-UV luminosity ratio ($L(\mathrm{H}\hat{\mathrm{I}}\pm )/L(\mathrm{UV})$) is often used to probe SFHs of star-forming galaxies and it is important to validate it against other proxies for burstiness. To address this issue, we present a statistical analysis of the resolved distribution of $\hat{I}{\pounds }_{\mathrm{SFR}}$ as well as stellar age and their correlations with the globally measured $L(\mathrm{H}\hat{\mathrm{I}}\pm )/L(\mathrm{UV})$ for a sample of 310 star-forming galaxies in two redshift bins of $1.37<z<1.70$ and $2.09<z<2.61$ observed by the MOSDEF survey. We use the multi-waveband CANDELS/3D-HST imaging of MOSDEF galaxies to construct $\hat{I}{\pounds }_{\mathrm{SFR}}$ and stellar age maps. We analyze the composite rest-frame far-UV spectra of a subsample of MOSDEF targets obtained by the Keck/LRIS, which includes 124 star-forming galaxies (MOSDEF-LRIS) at redshifts $1.4<z<2.6$, to examine the average stellar population properties, and the strength of age-sensitive FUV spectral features in bins of $L(\mathrm{H}\hat{\mathrm{I}}\pm )/L(\mathrm{UV})$. Our results show no significant evidence that individual galaxies with higher $L(\mathrm{H}\hat{\mathrm{I}}\pm )/L(\mathrm{UV})$ are undergoing a burst of star formation based on the resolved distribution of $\hat{I}{\pounds }_{\mathrm{SFR}}$ of individual star-forming galaxies. We segregate the sample into subsets with low and high $L(\mathrm{H}\hat{\mathrm{I}}\pm )/L(\mathrm{UV})$. The high-$L(\mathrm{H}\hat{\mathrm{I}}\pm )/L(\mathrm{UV})$ subset exhibits, on average, an age of $\log [Age/yr]$ = 8.0, compared to $\log [Age/yr]$ = 8.4 for the low-$L(\mathrm{H}\hat{\mathrm{I}}\pm )/L(\mathrm{UV})$ galaxies, though the difference in age is significant at only the $2\ddot{I}ƒ$ level. Furthermore, we find no variation in the strengths of Siiv$\hat{I}»\lambda 1393,1402$ and Civ$\hat{I}»\lambda 1548,1550$ P-Cygni features from massive stars between the two subsamples.

16 pages, 10 figures, published by the Monthly Notices of the Royal Astronomical Society