分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a study of seven spectroscopically confirmed (Ly$\alpha$ emitting) galaxies at redshift $z\simeq6$ using the $JWST$/NIRCam imaging data. These galaxies, with a wide range of Ly$\alpha$ luminosities, were recently observed in a series of NIRCam broad- and medium-bands. We constrain the rest-frame UV/optical continua and measure the H$\alpha$ line emission of the galaxies using the combination of the $JWST$/NIRCam and archival $HST$/WFC3 infrared photometry. We further estimate their escape fractions of Ly$\alpha$ photons ($f_{\rm esc}^{\rm Ly\alpha}$) and the production efficiency of ionizing photons ($\xi_{\rm ion}$). Among the sample, 6/7 galaxies have Ly$\alpha$ escape fractions of ${\lesssim}10\%$, which might be the status for most of star-forming galaxies at $z\simeq6$. One UV-faint Ly$\alpha$ galaxy with an extremely blue UV slope owns a large value of $f_{\rm esc}^{\rm Ly\alpha}$ reaching ${\simeq}50\%$. These galaxies spread a broad range of $\xi_{\rm ion}$ over log$_{10}$ $\xi_{\rm ion, 0}$ (Hz erg$^{-1}$) $\sim25.0-26.5$. We find that UV-fainter galaxies with bluer UV continuum slopes likely have higher escape fractions of Ly$\alpha$ photons. We also find that galaxies with higher Ly$\alpha$ line emission tend to produce ionizing photons more efficiently. The most Ly$\alpha$-luminous galaxy in the sample has a very high $\xi_{\rm ion, 0}$ of log$_{10}$ $\xi_{\rm ion, 0}$ (Hz erg$^{-1}$) $>26$. Our results support that Ly$\alpha$ galaxies may have served as an important contributor to the cosmic reionization. Blue and bright Ly$\alpha$ galaxies are excellent targets for $JWST$ follow-up spectroscopic observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a study of seven spectroscopically confirmed (Ly$\alpha$ emitting) galaxies at redshift $z\simeq6$ using the $JWST$/NIRCam imaging data. These galaxies, with a wide range of Ly$\alpha$ luminosities, were recently observed in a series of NIRCam broad- and medium-bands. We constrain the rest-frame UV/optical continua and measure the H$\alpha$ line emission of the galaxies using the combination of the $JWST$/NIRCam and archival $HST$/WFC3 infrared photometry. We further estimate their escape fractions of Ly$\alpha$ photons ($f_{\rm esc}^{\rm Ly\alpha}$) and the production efficiency of ionizing photons ($\xi_{\rm ion}$). Among the sample, 6/7 galaxies have Ly$\alpha$ escape fractions of ${\lesssim}10\%$, which might be the status for most of star-forming galaxies at $z\simeq6$. One UV-faint Ly$\alpha$ galaxy with an extremely blue UV slope owns a large value of $f_{\rm esc}^{\rm Ly\alpha}$ reaching ${\simeq}50\%$. These galaxies spread a broad range of $\xi_{\rm ion}$ over log$_{10}$ $\xi_{\rm ion, 0}$ (Hz erg$^{-1}$) $\sim25.0-26.5$. We find that UV-fainter galaxies with bluer UV continuum slopes likely have higher escape fractions of Ly$\alpha$ photons. We also find that galaxies with higher Ly$\alpha$ line emission tend to produce ionizing photons more efficiently. The most Ly$\alpha$-luminous galaxy in the sample has a very high $\xi_{\rm ion, 0}$ of log$_{10}$ $\xi_{\rm ion, 0}$ (Hz erg$^{-1}$) $>26$. Our results support that Ly$\alpha$ galaxies may have served as an important contributor to the cosmic reionization. Blue and bright Ly$\alpha$ galaxies are excellent targets for $JWST$ follow-up spectroscopic observations.
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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