First Peek with JWST/NIRCam Wide-Field Slitless Spectroscopy: Serendipitous Discovery of a Strong [O III]/H$\alpha$ Emitter at $z=6.11$

Abstract

We report the serendipitous discovery of an [O III] $\lambda \lambda$4959/5007 and H$\alpha$ line emitter in the Epoch of Reionization (EoR) with the JWST commissioning data taken in the NIRCam wide field slitless spectroscopy (WFSS) mode. Located $\sim$55" away from the flux calibrator P330-E, this galaxy exhibits bright [O III] $\lambda \lambda$4959/5007 and H$\alpha$ lines detected at 3.7, 9.9 and 5.7$\sigma$, respectively, with a spectroscopic redshift of $z=6.112\pm 0.001$. The total H$\beta$+[O III] equivalent width is 664$\pm$98 Å (454$\pm$78 Å from the [O III] $\lambda$5007 line). This provides direct spectroscopic evidence for the presence of strong rest-frame optical lines (H$\beta$+[O III] and H$\alpha$) in EoR galaxies as inferred previously from the analyses of Spitzer/IRAC spectral energy distributions. Two spatial and velocity components are identified in this source, possibly indicating that this system is undergoing a major merger, which might have triggered the ongoing starburst with strong nebular emission lines over a timescale of $\sim$2 Myr as our SED modeling suggests. The tentative detection of He II $\lambda$4686 line ($1.9\sigma$), if real, may indicate the existence of very young and metal-poor star-forming regions with a hard UV radiation field. Finally, this discovery demonstrates the power and readiness of the JWST/NIRCam WFSS mode, and marks the beginning of a new era for extragalactic astronomy, in which EoR galaxies can be routinely discovered via blind slitless spectroscopy through the detection of rest-frame optical emission lines.

10 pages, 4 figures, published in the ApJL

References in corpus (10)

• Galaxies with Wolf-Rayet signatures in the low-redshift Universe - A survey using the Sloan Digital Sky Survey
• Galaxy Formation and Reionization: Key Unknowns and Expected Breakthroughs by the James Webb Space Telescope
• Ultraviolet spectra of extreme nearby star-forming regions --- approaching a local reference sample for JWST
• High-precision Photometric Redshifts from Spitzer/IRAC: Extreme [3.6]-[4.5] Colors Identify Galaxies in the Redshift Range z~6.6-6.9
• The GREATS H$\beta$+[OIII] Luminosity Function and Galaxy Properties at $\mathbf{z}\sim 8$: Walking the Way of JWST
• ALMA reveals metals yet no dust within multiple components in CR7
• MMT Spectroscopy of Lyman-alpha at z$\simeq$7: Evidence for Accelerated Reionization Around Massive Galaxies
• The formation of UCDs and massive GCs: Quasar-like objects for testing for a variable stellar initial mass function (IMF)
• Active Galactic Nuclei from HeII: a more complete census of AGN in SDSS galaxies yields a new population of low-luminosity AGN in highly star-forming galaxies
• Luminous Lyman-alpha Emitters with Very Blue UV-continuum Slopes at Redshift 5.7 <= z <= 6.6

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