Browsing by Author "Wang, Junxian "

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    A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger
    (2019) Xue, Yongquan; Zheng, X. C.; Li, Y.; Brandt, W. N.; Zhang, Bryna; Luo, Bruce; Zhang, Boce; Bauer, Franz Erik; Sun, H.; Lehmer, B. D.; Wu, Xuefeng; Yang, Guang; Kong, Xu; Li, J. Y.; Sun, M. Y.; Wang, Junxian; Vito, Fabio
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    Discovery of Local Analogs to JWST's Little Red Dots
    (2024) Lin, Ruqiu; Zheng, Zhen-Ya; Jiang, Chunyan; Yuan, Fang-Ting; Ho, Luis C.; Wang, Junxian; Jiang, Linhua; Rhoads, James E.; Malhotra, Sangeeta; Barrientos, Luis Felipe; Wold, Isak; Infante Lira, Leopoldo; Zhu, Shuairu; Ji, Xiang; Fu, Xiaodan
    Recently, the James Webb Space Telescope (JWST) has revealed a new class of high redshift (high- z , z > 4) compact galaxies which are red in the rest-frame optical and blue in the rest-frame UV as V-shaped spectral energy distributions (SEDs), referred to as “Little Red Dots” (LRDs). It is very likely that LRDs host obscured broad-line active galactic nuclei (AGNs). In the meanwhile, Green pea galaxies (GPs), which are compact dwarf galaxies at low redshift, share various similar properties with high redshift star-forming galaxies. Here we aim to find the connection between the LRDs and GPs hosting broad-line AGNs (BLGPs). With a sample of 19 BLGPs obtained from our previous work, we further identify 7 GPs with V-shaped rest-frame UV-to-optical SEDs that are likely local analogs to LRDs. These V-shaped BLGPs exhibit faint UV absolute magnitudes and sub-Eddington rates similar to those of LRDs. Three of them occupy a similar region as LRDs in the BPT diagram, suggesting they have similar ionization conditions and gas-phase metallicities to LRDs. These similarities suggest that V-shaped BLGPs can be taken as local analogs of high-redshift LRDs. In addition, most (16/19) BLGPs, including 6 V-shaped BLGPs, host over-massive black holes above the local M BH- M∗ relation, making it the first sample of galaxies hosting over-massive black holes at z < 0.4. These findings will help us learn more about the formation and co-evolution of early galaxies and black holes.
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    GREEN PEA GALAXIES REVEAL SECRETS OF Ly alpha ESCAPE
    (IOP PUBLISHING LTD, 2016) Yang, Huan; Malhotra, Sangeeta; Gronke, Max; Rhoads, James E.; Dijkstra, Mark; Jaskot, Anne; Zheng, Zhenya; Wang, Junxian
    We analyze archival Ly alpha spectra of 12 "Green Pea" galaxies observed with the Hubble Space Telescope, model their Ly alpha profiles with radiative transfer models, and explore the dependence of the Ly alpha escape fraction on various properties. Green Pea galaxies are nearby compact starburst galaxies with [O III] lambda 5007 equivalent widths (EWs) of hundreds of angstrom. All 12 Green Pea galaxies in our sample show Ly alpha lines in emission, with an Ly alpha EW distribution similar to high-redshift Ly alpha emitters. Combining the optical and UV spectra of Green Pea galaxies, we estimate their Ly alpha escape fractions and find correlations between Ly alpha escape fraction and kinematic features of Ly alpha profiles. The escape fraction of Ly alpha in these galaxies ranges from 1.4% to 67%. We also find that the Ly alpha escape fraction depends strongly on metallicity and moderately on dust extinction. We compare their high-quality Ly alpha profiles with single H I shell radiative transfer models and find that the Ly alpha escape fraction anticorrelates with the derived H I column densities. Single-shell models fit most Ly alpha profiles well, but not the ones with the. highest escape fractions of Ly alpha. Our results suggest that low H I column density and low metallicity are essential for Ly alpha escape. and make a galaxy an Ly alpha emitter.
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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.