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Title: Resolved star formation on sub-galactic scales in a merger at z = 1.7

We present a detailed analysis of Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) G141 grism spectroscopy for seven star-forming regions of the highly magnified lensed starburst galaxy RCSGA 032727-132609 at z = 1.704. We measure the spatial variations of the extinction in RCS0327 through the observed Hγ/Hβ emission line ratios, finding a constant average extinction of E(B – V){sub gas} = 0.40 ± 0.07. We infer that the star formation is enhanced as a result of an ongoing interaction, with measured star formation rates derived from demagnified, extinction-corrected Hβ line fluxes for the individual star-forming clumps falling >1-2 dex above the star formation sequence. When combining the HST/WFC3 [O III] λ5007/Hβ emission line ratio measurements with [N II]/Hα line ratios from Wuyts et al., we find that the majority of the individual star-forming regions fall along the local 'normal' abundance sequence. With the first detections of the He I λ5876 and He II λ4686 recombination lines in a distant galaxy, we probe the massive-star content of the star-forming regions in RCS0327. The majority of the star-forming regions have a He I λ5876 to Hβ ratio consistent with the saturated maximum value, which is only possible if they stillmore » contain hot O-stars. Two regions have lower ratios, implying that their last burst of new star formation ended ∼5 Myr ago. Together, the He I λ5876 and He II λ4686 to Hβ line ratios provide indirect evidence for the order in which star formation is stopping in individual star-forming knots of this high-redshift merger. We place the spatial variations of the extinction, star formation rate and ionization conditions in the context of the star formation history of RCS0327.« less
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States)
  2. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  3. The Department of Astronomy and Astrophysics, and the Kavli Institute for Cosmological Physics, The University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)
  4. Department of Astronomy and Astrophysics, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)
  5. Max-Planck-Institut für Extraterrestrische Physik (MPE), Giessenbachstr., D-85748 Garching (Germany)
Publication Date:
OSTI Identifier:
22365460
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 790; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; DETECTION; EMISSION; GALAXIES; GRAVITATIONAL LENSES; INTERACTIONS; RECOMBINATION; RED SHIFT; SPACE; SPECTROSCOPY; STARS; TELESCOPES; VARIATIONS