分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We report the detection of Lyman Continuum (LyC) emission from the galaxy, CDFS-6664, at z=3.797 in a sample of Lyman break galaxies with detected [OIII] emission lines. The LyC emission is detected with a significance ~$5\sigma$ in the F336W band of the Hubble Deep UV Legacy Survey, corresponding to the 650-770 Angstrom rest-frame. The light centroid of the LyC emission is offset from the galaxy center by about 0.2" (1.4 pkpc). The Hubble deep images at longer wavelengths show that the emission is unlikely provided by low-redshift interlopers. The photometric and spectroscopic data show that the possible contribution of an active galactic nucleus is quite low. Fitting the spectral energy distribution of this source to stellar population synthesis models, we find that the galaxy is young (~50 Myr) and actively forming stars with a rate of 52.1$\pm$4.9 $M_{\odot}\mathrm{yr^{-1}}$. The significant star formation and the spatially offset LyC emission support a scenario where the ionizing photons escape from the low-density cavities in the ISM excavated by massive young stars. From the nebular model, we estimate the escape fraction of LyC photons to be 38$\pm$7% and the corresponding IGM transmission to be 60%, which deviates more than 3$\sigma$ from the average transmission. The unusually high IGM transmission of LyC photons in CDFS-6664 may be related to a foreground type-2 quasar, CDF-202, at z=3.7, with a projected separation of 1.2' only. The quasar may have photoevaporated optically thick absorbers and enhance the transmission on the sightline of CDFS-6664.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
P. T. Rahna
Zhen-Ya Zheng
Ana L. Chies-Santos
Zheng Cai
Daniele Spinoso
Isabel Marquez
Roderik Overzier
L. Raul Abramo
Silvia Bonoli
Carolina Kehrig
L. A. Diaz-Garcia
Mirjana Povic
Roberto Soria
Jose M. Diego
Tom Broadhurst
Rosa M. Gonzalez Delgado
Jailson Alcaniz
Narciso Benitez
Saulo. Carneiro
A. Javier Cenarro
摘要： The Ly$\alpha$ emission is an important tracer of neutral gas in a circum-galactic medium (CGM) around high-z QSOs. The origin of Lya emission around QSOs is still under debate which has significant implications for galaxy formation and evolution. In this paper, we study Ly$\alpha$ nebulae around two high redshift QSOs, SDSS J141935.58+525710.7 at $z=3.218$ (hereafter QSO1) and SDSS J141813.40+525240.4 at $z=3.287$ (hereafter QSO2), from the miniJPAS survey within the AEGIS field. Using the contiguous narrow-band (NB) images from the miniJPAS survey and SDSS spectra, we analyzed their morphology, nature, and origin. We report the serendipitous detection of double-core Ly\almorphology around two QSOs which is rarely seen among other QSOs. The separations of the two Ly\al~cores are 11.07 $\pm$ 2.26 kpcs (1.47 $\pm$ 0.3$^{\prime\prime}$) and 9.73 $\pm$ 1.55 kpcs (1.31 $\pm$ 0.21$^{\prime\prime}$) with Ly$\alpha$~line luminosities of $\sim$ 3.35 $\times 10^{44}$ erg s $^{-1} $ and $\sim$ 6.99 $\times$ 10$^{44}$ erg s $^{-1}$ for QSO1 and QSO2, respectively. The miniJPAS NB images show evidence of extended Ly$\alpha$ and CIV morphology for both QSOs and extended HeII morphology for QSO1. These two QSOs may be potential candidates for the new enormous Lyman alpha nebula (ELAN) found from the miniJPAS survey due to their extended morphology in the shallow depth and relatively high Ly$\alpha$ luminosities. We suggest that galactic outflows are the major powering mechanism for the double-core Ly$\alpha$ morphology. Considering the relatively shallow exposures of miniJPAS, the objects found here could be the tip of the iceberg of a promising number of such objects that will be uncovered in the upcoming full J-PAS survey and deep IFU observations with 8-10m telescopes will be essential for constraining the underlying physical mechanism that is responsible for the double-cored morphology.
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