Browsing by Author "Wold, Isak G. B."

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    LAGER Lyα Luminosity Function at z ∼ 7: Implications for Reionization
    (2022) Wold, Isak G. B. ; Malhotra, Sangeeta ; Rhoads, James ; Wang, Junxian ; Hu, Weida ; Perez, Lucia A. ; Zheng, Zhen-Ya ; Khostovan, Ali Ahmad ; Walker, Alistair R. ; Barrientos, L. Felipe ; González-López, Jorge ; Harish, Santosh ; Infante, Leopoldo ; Jiang, Chunyan ; Pharo, John ; Moya-Sierralta, Cristóbal ; Bauer, Franz E. ; Galaz, Gaspar ; Valdes, Francisco ; Yang, Huan
    We present a new measurement of the Ly alpha luminosity function (LF) at redshift z = 6.9, finding moderate evolution from z = 5.7 that is consistent with a fully or largely ionized z similar to 7 intergalactic medium. Our result is based on four fields of the LAGER (Lyman Alpha Galaxies in the Epoch of Reionization) project. Our survey volume of 6.1 x 10(6) Mpc(3) is double that of the next largest z similar to 7 survey. We combine two new LAGER fields (WIDE12 and GAMA15A) with two previously reported LAGER fields (COSMOS and CDFS). In the new fields, we identify N = 95 new z = 6.9 Ly alpha emitter (LAEs) candidates, characterize our survey's completeness and reliability, and compute Ly alpha LFs. The best-fit Schechter LF parameters for all four LAGER fields are in good general agreement. Two fields (COSMOS and WIDE12) show evidence for a bright-end excess above the Schechter function fit. We find that the Ly alpha luminosity density declines at the same rate as the UV continuum LF from z = 5.7 to 6.9. This is consistent with an intergalactic medium that was fully ionized as early as redshift z similar to 7 or with a volume-averaged neutral hydrogen fraction of x (H I) < 0.33 at 1 sigma.
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    New Spectroscopic Confirmations of Lyα Emitters at Z ∼ 7 from the LAGER Survey
    (2022) Harish, Santosh; Wold, Isak G. B.; Malhotra, Sangeeta; Rhoads, James E.; Hu, Weida; Wang, Junxian; Zheng, Zhen-ya; Barrientos, L. Felipe; Gonzalez-Lopez, Jorge; Perez, Lucia A.; Khostovan, Ali Ahmad; Infante, Leopoldo; Jiang, Chunyan; Moya-Sierralta, Cristobal; Pharo, John; Valdes, Francisco; Yang, Huan
    We report spectroscopic confirmations of 15 Ly alpha galaxies at z similar to 7, implying a spectroscopic confirmation rate of similar to 80% on candidates selected from the Ly alpha Galaxies in the Epoch of Reionization (LAGER), which is the largest (24 deg(2)) survey aimed at finding Ly alpha emitters (LAEs) at z similar to 7 and uses deep narrowband imaging from the Dark Energy Camera at CTIO. LAEs at high redshifts are sensitive probes of cosmic reionization, and narrowband imaging is a robust and effective method for selecting a large number of LAEs. In this work, we present results from the spectroscopic follow-up of LAE candidates in two LAGER fields, COSMOS and WIDE-12, using observations from Keck/LRIS. We report the successful detection of Ly alpha emission in 15 candidates. Three of these in COSMOS have matching confirmations from a previous spectroscopic follow-up and are part of the overdense region, LAGER-z7OD1. Two other candidates that were not detected with LRIS have prior spectroscopic confirmations from Magellan. Including these, we obtain a spectroscopic confirmation success rate of similar to 80% for LAGER LAE candidates. Thorough checks were performed to reject the possibility of these detections being foreground emission resulting with a probability of, at most, one contaminant. We do not detect any other UV nebular lines in our LRIS spectra, apart from Ly alpha. We estimate a 2 sigma upper limit for the ratio of N v/Ly alpha, f (NV)/f (Ly alpha ) less than or similar to 0.27. Including confirmations from this work, a total of 33 LAE sources from LAGER are now spectroscopically confirmed. LAGER has more than doubled the sample of spectroscopically confirmed LAE sources at z similar to 7.