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Your search keyword '"Man Cheung Alex Li"' showing total 3 results
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3 results on '"Man Cheung Alex Li"'

1. A Lens Finder Map to Check Claimed High-z Galaxies behind SMACS J0723.3-7327

Author

Alex Chow, Sung Kei Li, Jeremy Lim, Tom Broadhurst, Man Cheung Alex Li, James Nianias, Jake Summers, and Rogier Windhorst

Subjects
Strong gravitational lensing, Galaxy clusters, Astrophysics, QB460-466
Abstract

The first science image released by the James Webb Space Telescope (JWST) reveals numerous galaxies in the distant background of the galaxy cluster SMACS J0723.3-7327. Some have claimed redshifts of up to z ≃ 20, challenging standard cosmological models for structure formation. Here, we present a lens model for SMACS J0723.3-7327 anchored on five spectroscopically confirmed systems at 1.38 ≤ z ≤ 2.21 that are multiply lensed, along with 12 other systems with proposed image counterparts sharing common colors, spectral energy distributions, and morphological features, but having unknown redshifts. Constrained only by their image positions, and where available, redshifts, our lens model correctly reproduces the positions and correctly predicts the morphologies and relative brightnesses of all these image counterparts, as well as providing geometrically determined redshifts spanning 1.4 ≲ z ≲ 6.7 for the 12 candidate multiply lensed galaxies lacking spectroscopic measurements. From this lens model, we create a lens finder map that defines regions over which galaxies beyond a certain redshift are predicted to be multiply lensed. Applying this map to three galaxies claimed to be at 10 ≲ z ≲ 20, we find no image counterparts at locations (with an uncertainty of ∼0.″5) where they ought to be sufficiently magnified to be detectable—suggesting instead that these galaxies lie at z ≲ 1.7–3.2. In lieu of spectroscopy, the creation of reliable lens finder maps for cluster fields is urgently needed to test and constrain redshifts inferred from photometry for a rapidly increasing number of candidate high- z galaxies found with JWST.

Published
2024
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2. KMT-2021-BLG-0171Lb and KMT-2021-BLG-1689Lb: Two Microlensing Planets in the KMTNet High-Cadence Fields With Followup Observations

Author

Hongjing Yang, Weicheng Zang, Andrew Gould, Jennifer C Yee, Kyu-Ha Hwang, Grant Christie, Takahiro Sumi, Jiyuan Zhang, Shude Mao, Michael D Albrow, Sun-Ju Chung, Cheongho Han, Youn Kil Jung, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W Pogge, John Drummond, Dan Maoz, Jennie McCormick, Tim Natusch, Matthew T Penny, Wei Zhu, Ian A Bond, Fumio Abe, Richard Barry, David P Bennett, Aparna Bhattacharya, Martin Donachie, Hirosane Fujii, Akihiko Fukui, Yuki Hirao, Yoshitaka Itow, Rintaro Kirikawa, Iona Kondo, Naoki Koshimoto, Man Cheung Alex Li, Yutaka Matsubara, Yasushi Muraki, Shota Miyazaki, Greg Olmschenk, Clément Ranc, Nicholas J Rattenbury, Yuki Satoh, Hikaru Shoji, Stela Ishitani Silva, Daisuke Suzuki, Yuzuru Tanaka, Paul J Tristram, Tsubasa Yamawaki, and Atsunori Yonehara

Subjects
Astronomy
Abstract

Follow-up observations of high-magnification gravitational microlensing events can fully exploit their intrinsic sensitivity to detect extrasolar planets, especially those with small mass ratios. To make followup observations more uniform and efficient, we develop a system, HighMagFinder, to automatically alert possible ongoing high-magnification events based on the real-time data from the Korea Microlensing Telescope Network (KMTNet). We started a new phase of follow-up observations with the help of HighMagFinder in 2021. Here we report the discovery of two planets in high-magnification microlensing events, KMT- 2021-BLG-0171 and KMT-2021-BLG-1689, which were identified by the HighMagFinder. We find that both events suffer the ‘central-resonant’ caustic degeneracy. The planet-host mass-ratio is q ∼4.7 × 10−5 or q ∼2.2 × 10−5 for KMT-2021-BLG-0171, and q ∼2.5 × 10−4 or q ∼1.8 × 10−4 for KMT-2021-BLG-1689. Together with two other events, four cases that suffer such degeneracy have been discovered in the 2021 season alone, indicating that the de generate solutions may have been missed in some previous studies. We also propose a quantitative factor to weight the probability of each solution from the phase space. The resonant interpretations for the two events are disfavoured under this consideration. This factor can be included in future statistical studies to weight degenerate solutions.

Published
2022
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3. OGLE-2018-BLG-0799Lb: a q ∼ 2.7 × 10−3 planet with Spitzer parallax

Author

Weicheng Zang, Yossi Shvartzvald, Andrzej Udalski, Jennifer C Yee, Chung-Uk Lee, Takahiro Sumi, Xiangyu Zhang, Hongjing Yang, Shude Mao, Sebastiano Calchi Novati, Andrew Gould, Wei Zhu, Charles A Beichman, Geoffery Bryden, Sean Carey, B Scott Gaudi, Calen B Henderson, Przemek Mróz, Jan Skowron, Radoslaw Poleski, Michał K Szymański, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof Ulaczyk, Krzysztof A Rybicki, Patryk Iwanek, Marcin Wrona, Michael D Albrow, Sun-Ju Chung, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, In-Gu Shin, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W Pogge, Ian A Bond, Fumio Abe, Richard Barry, David P Bennett, Aparna Bhattacharya, Martin Donachie, Hirosane Fujii, Akihiko Fukui, Yuki Hirao, Yoshitaka Itow, Rintaro Kirikawa, Iona Kondo, Naoki Koshimoto, Man Cheung Alex Li, Yutaka Matsubara, Yasushi Muraki, Shota Miyazaki, Clément Ranc, Nicholas J Rattenbury, Yuki Satoh, Hikaru Shoji, Daisuke Suzuki, Yuzuru Tanaka, Paul J Tristram, Tsubasa Yamawaki, Atsunori Yonehara, Etienne Bachelet, Markus P G Hundertmark, R Figuera Jaimes, Dan Maoz, Matthew T Penny, Rachel A Street, and Yiannis Tsapras

Subjects
Space and Planetary Science, Astronomy and Astrophysics
Abstract

We report the discovery and analysis of a planet in the microlensing event OGLE-2018-BLG-0799. The planetary signal was observed by several ground-based telescopes, and the planet-host mass ratio is q = (2.65 ± 0.16) × 10−3. The ground-based observations yield a constraint on the angular Einstein radius θE, and the microlensing parallax vector $\boldsymbol{{\pi} }_{\rm E}$, is strongly constrained by the Spitzer data. However, the 2019 Spitzer baseline data reveal systematics in the Spitzer photometry, so there is ambiguity in the magnitude of the parallax. In our preferred interpretation, a full Bayesian analysis using a Galactic model indicates that the planetary system is composed of an $M_{\rm planet} = 0.26_{-0.11}^{+0.22}M_{\rm J}$ planet orbiting an $M_{\rm host} = 0.093_{-0.038}^{+0.082}~\mathrm{M}_{\odot }$, at a distance of $D_{\rm L} = 3.71_{-1.70}^{+3.24}$ kpc. An alternate interpretation of the data shifts the localization of the minima along the arc-shaped microlens parallax constraints. This, in turn, yields a more massive host with median mass of $0.13 {\, \mathrm{M}_{\odot }}$ at a distance of 6.3 kpc. This analysis demonstrates the robustness of the osculating circles formalism, but shows that further investigation is needed to assess how systematics affect the specific localization of the microlens parallax vector and, consequently, the inferred physical parameters.

Published
2022
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