• Corpus ID: 251881486

No Evidence of a Correlation between $\rm{H}\alpha$-to-UV Ratio and Burstiness for Typical Star-forming Galaxies at $z\sim2$

@inproceedings{Rezaee2022NoEO,
  title={No Evidence of a Correlation between \$\rm\{H\}\alpha\$-to-UV Ratio and Burstiness for Typical Star-forming Galaxies at \$z\sim2\$},
  author={Saeed Rezaee and Naveen A. Reddy and Michael W. Topping and Irene Shivaei and Alice E. Shapley and Tara Fetherolf and Mariska Kriek and Alison L. Coil and Bahram Mobasher and Brian D. Siana and Xinnan Du and Ali Ahmad Khostovan and Andrew Weldon and Najmeh Emami and Nima Chartab},
  year={2022}
}

• S. Rezaee, N. Reddy, +12 authors N. Chartab
• Published 25 August 2022
• Physics

It has long been uncertain how effective the dust-corrected H 𝛼 -to-UV luminosity ratio ( 𝐿 ( H 𝛼 )/ 𝐿 ( UV ) ) is in probing bursty star-formation histories (SFHs) for high-redshift galaxies. To address this issue, we present a statistical analysis of the resolved distribution of star-formation-rate surface density ( Σ SFR ) as well as stellar age and their correlations with the globally measured 𝐿 ( H 𝛼 )/ 𝐿 ( 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 MOSFIRE Deep Evolution Field (MOSDEF) survey. We use the multi-waveband CANDELS/3D-HST imaging of MOSDEF galaxies to construct Σ SFR and stellar age maps. We also analyze the composite rest-frame far-UV spectra of a subsample of MOSDEF targets obtained by the Keck Low Resolution Imager and Spectrometer (LRIS), which includes 124 star-forming galaxies at redshifts 1 . 4 < 𝑧 < 2 . 6, to examine the average stellar population properties, and the strength of extremely age-sensitive FUV spectral features in bins of 𝐿 ( H 𝛼 )/ 𝐿 ( UV ) . We find no evidence that galaxies with higher 𝐿 ( H 𝛼 )/ 𝐿 ( UV ) are undergoing a burst of star formation based on the distribution of Σ SFR and stellar age as well as the strengths of Si iv 𝜆𝜆 1393 , 1402 and C iv 𝜆𝜆 1548 , 1550 P-Cygni features from massive stars. Our results suggest that the 𝐿 ( H 𝛼 )/ 𝐿 ( UV ) ratio is not a reliable tracer of bursty SFHs for typical star-forming galaxies at high redshift. We also study the variations observed in the strength of the nebular He ii 𝜆 1640 emission between the 𝐿 ( H 𝛼 )/ 𝐿 ( UV ) subsamples. We find that variations in the upper-mass limit of the IMF cannot fully account for all the observed difference in the HeII emission between the 𝐿 ( H 𝛼 )/ 𝐿 ( UV ) subsamples, and that another source of He + ionizing photons, such as X-ray binaries, may be needed to explain such a difference.