Browsing by Author "Rhoads, J."

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    A lack of Lyman α emitters within 5 Mpc of a luminous quasar in an overdensity at z=6.9: Potential evidence of negative quasar feedback at protocluster scales
    (2024) Lambert, Trystan S.; Assef, R. J.; Mazzucchelli, C.; Banados, E.; Aravena, M.; Barrientos, F.; Gonzalez-Lopez, J.; Hu, W.; Infante, L.; Malhotra, S.; Moya-Sierralta, C.; Rhoads, J.; Valdes, F.; Wang, J.; Wold, I. G. B.; Zheng, Z.
    High-redshift quasars are thought to live in the densest regions of space, which should be made evident by an overdensity of galaxies around them. However, campaigns to identify these overdensities by searching for Lyman-break galaxies (LBGs) and Lyman alpha emitters (LAEs) have had mixed results. These may be explained by either the small field of view of some of the experiments, the broad redshift ranges targeted by LBG searches, and the inherently high uncertainty of quasar redshifts estimated from ultraviolet emission lines, which makes it difficult to place the Ly-alpha emission line within a narrowband filter. Here, we present a 3 square degree search (similar to 1000 pMpc(2)) for LAEs around the z = 6.9 quasar VIK J2348-3054 using the Dark Energy CAMera (DECam) housed on the 4m Blanco telescope, finding 38 LAEs. The systemic redshift of VIK J2348-3054 is known from ALMA [CII] observations and places the Ly-alpha emission line of companions within the NB964 narrowband of DECam. This is the largest field-of-view LAE search around a z > 6 quasar conducted to date. We find that this field is similar to ten times more overdense than Chandra Deep-Field South, observed previously with the same instrumental setup as well as several combined blank fields. This is strong evidence that VIK J2348-3054 resides in an overdensity of LAEs over several Mpc. Surprisingly, we find a lack of LAEs within 5 physical Mpc of the quasar and take this to most likely be evidence of quasar-suppressing star formation in its immediate vicinity. This result highlights the importance of performing overdensity searches over large areas to properly assess the density of those regions of the Universe.
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    A resolved Lyman α profile with doubly peaked emission at z∼7
    (EDP Sciences, 2024) Moya Sierralta, Cristobal; González López, Jorge; Infante Lira Leopoldo; Barrientos Parra, Luis Felipe; Hu, W.; Malhotra, S.; Rhoads, J.; Wang, J.; Wold, I.; Zheng, Z.
    © The Authors 2024.Context. The epoch of reionization is a landmark in structure formation and galaxy evolution. How it happened is still not clear, especially regarding which population of objects was responsible for contributing the bulk of ionizing photons to this process. Doubly peaked Lyman-alpha profiles in this epoch are of particular interest since they hold information about the escape of ionizing radiation and the environment surrounding the source. Aims. We wish to understand the escape mechanisms of ionizing radiation in Lyα emitters during this time and the origin of a doubly peaked Lyman-alpha profile. We also wish to estimate the size of a potential ionized bubble. Methods. Using radiative transfer models, we fit the line profile of a bright Lyα emitter at z-≈-6.9 using various gas geometries. The line modeling reveals significant radiation escape from this system. Results. The studied source shows significant escape (fesc(Lyα) ≈ 0.8, as predicted by the best fitting radiative transfer model) and appears to inhabit an ionized bubble of radius Rb-0.8-0.3+0.5-pMpc(tage/108)1/3. Radiative transfer modeling predicts the line to be completely redward of the systemic redshift. We suggest the line morphology is produced by inflows, by multiple components emitting Lyα, or by an absorbing component in the red wing. Conclusions. We propose that CDFS-1-s profile has two red peaks produced by winds within the system. Its high fesc(Lyα) and the low-velocity offset from the systemic redshift suggest that the source is an active ionizing agent. Future observations will reveal whether a peak is present blueward of the systemic redshift or if multiple components produce the profile.
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    CONSTRAINING THE Lyα ESCAPE FRACTION WITH FAR- INFRARED OBSERVATIONS OF Lyα EMITTERS
    (2014) Wardlow, Julie L.; Malhotra, S.; Zheng, Z.; Finkelstein, S.; Bock, J.; Bridge, C.; Calanog, J.; Ciardullo, R.; Conley, A.; Cooray, A.; Farrah, D.; Gawiser, E.; Gronwall, C.; Heinis, S.; Ibar, E.; Ivison, R. J.; Marsden, G.; Oliver, S. J.; Rhoads, J.; Riechers, D.; Schulz, B.; Smith, A. J.; Viero, M.; Wang, L.; Zemcov, M.
    We study the far-infrared properties of 498 Ly alpha emitters (LAEs) at z = 2.8, 3.1, and 4.5 in the Extended Chandra Deep Field-South, using 250, 350, and 500 mu m data from the Herschel Multi-tiered Extragalactic Survey and 870 mu m data from the LABOCA ECDFS Submillimeter Survey. None of the 126, 280, or 92 LAEs at z = 2.8, 3.1, and 4.5, respectively, are individually detected in the far-infrared data. We use stacking to probe the average emission to deeper flux limits, reaching 1 sigma depths of similar to 0.1 to 0.4 mJy. The LAEs are also undetected at >= 3 sigma in the stacks, although a 2.5 sigma signal is observed at 870 mu m for the z = 2.8 sources. We consider a wide range of far-infrared spectral energy distributions (SEDs), including an M82 and an Sd galaxy template, to determine upper limits on the far-infrared luminosities and far-infrared-derived star formation rates of the LAEs. These star formation rates are then combined with those inferred from the Ly alpha and UV emission to determine lower limits on the LAEs' Lya escape fraction (f(esc)(Ly alpha)). For the Sd SED template, the inferred LAEs fesc(Ly alpha) are greater than or similar to 30% (1 sigma) at z = 2.8, 3.1, and 4.5, which are all significantly higher than the global fesc(Ly alpha) at these redshifts. Thus, if the LAEs fesc(Ly alpha) follows the global evolution, then they have warmer far-infrared SEDs than the Sd galaxy template. The average and M82 SEDs produce lower limits on the LAE fesc(Ly alpha) of similar to 10%-20% (1 sigma), all of which are slightly higher than the global evolution of fesc(Ly alpha), but consistent with it at the 2 sigma-3 sigma level.
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    First Results from the Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) Survey: Cosmological Reionization at z similar to 7
    (2017) Zheng, Z. Y.; Wang, J. X.; Rhoads, J.; Infante Lira, Leopoldo; Malhotra, S.; Hu, W. D.; Walker, A. R.; Jiang, L. H.; Jiang C. Y.; Hibon, P.; Gonzalez, A.; Kong, X. U.; Zheng, X. Z.; Galaz, Gaspar; Barrientos, L. F.; Zheng, Z. Y.; Wang, J. X.; Rhoads, J.; Infante Lira, Leopoldo; Malhotra, S.; Hu, W. D.; Walker, A. R.; Jiang, L. H.; Jiang C. Y.; Hibon, P.; Gonzalez, A.; Kong, X. U.; Zheng, X. Z.; Galaz, Gaspar; Barrientos, Luis Felipe; Zheng, Z. Y.; Wang, J. X.; Rhoads, J.; Infante Lira, Leopoldo; Malhotra, S.; Hu, W. D.; Walker, A. R.; Jiang, L. H.; Jiang C. Y.; Hibon, P.; Gonzalez, A.; Kong, X. U.; Zheng, X. Z.; Galaz, Gaspar; Barrientos, Luis Felipe