The Origins of UV-optical Color Gradients in Star-forming Galaxies at z ∼ 2: Predominant Dust Gradients but Negligible sSFR Gradients

F. S. Liu, Dongfei Jiang, S M {Faber}, David C. Koo, Hassen M. Yesuf, Sandro Tacchella, Shude Mao, Weichen Wang, Yicheng Guo, Jerome J. Fang, Guillermo Barro, Xianzhong Zheng, Meng Jia, Wei Tong, Lu Liu, Xianmin Meng

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The rest-frame UV-optical (i.e., NUV - B) color is sensitive to both low-level recent star formation (specific star formation rate-sSFR) and dust. In this Letter, we extend our previous work on the origins of NUV - B color gradients in star-forming galaxies (SFGs) at z ∼ 1 to those at z ∼ 2. We use a sample of 1335 large (semimajor axis radius RSMA> 0. 18) SFGs with extended UV emission out to 2RSMA in the mass range M∗= 109- 1011 M⊙ at1.5 < z < 2.8 in the CANDELS/GOODS-S and UDS fields. We show that these SFGs generally have negative NUV - B color gradients (redder centers), and their color gradients strongly increase with galaxy mass. We also show that the global rest-frame FUV - NUV color is approximately linear with AV, which is derived by modeling the observed integrated FUV to NIR spectral energy distributions of the galaxies. Applying this integrated calibration to our spatially resolved data, we find a negative dust gradient (more dust extinguished in the centers), which steadily becomes steeper with galaxy mass. We further find that the NUV - B color gradients become nearly zero after correcting for dust gradients regardless of galaxy mass. This indicates that the sSFR gradients are negligible and dust reddening is likely the principal cause of negative UV-optical color gradients in these SFGs. Our findings support that the buildup of the stellar mass in SFGs at Cosmic Noon is self-similar inside 2RSMA.

    Original languageEnglish
    Article numberL2
    JournalAstrophysical Journal Letters
    Volume844
    Issue number1
    DOIs
    Publication statusPublished - 14 Jul 2017

    Keywords

    • galaxies: high-redshift
    • galaxies: photometry
    • galaxies: star formation

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