Geoff C-F Chen's research while affiliated with University of California, Los Angeles and other places
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Publications (6)
Strongly lensed quasars can provide measurements of the Hubble constant (H0) independent of any other methods. One of the key ingredients is exquisite high-resolution imaging data, such as Hubble Space Telescope (HST) imaging and adaptive-optics (AO) imaging from ground-based telescopes, which provide strong constraints on the mass distribution of...
Astrometric precision and knowledge of the point spread function are key ingredients for a wide range of astrophysical studies including time-delay cosmography in which strongly lensed quasar systems are used to determine the Hubble constant and other cosmological parameters. Astrometric uncertainty on the positions of the multiply-imaged point sou...
We present the lens mass model of the quadruply-imaged gravitationally lensed quasar WFI2033 − 4723, and perform a blind cosmographical analysis based on this system. Our analysis combines (1) time-delay measurements from 14 yr of data obtained by the COSmological MOnitoring of GRAvItational Lenses (COSMOGRAIL) collaboration, (2) high-resolution Hu...
We present a measurement of the Hubble constant (H0) and other cosmological parameters from a joint analysis of six gravitationally lensed quasars with measured time delays. All lenses except the first are analyzed blindly with respect to the cosmological parameters. In a flat ΛCDM cosmology, we find $H_{0} = 73.3_{-1.8}^{+1.7}~\mathrm{km~s^{-1}~Mp...
We present the measurement of the Hubble constant, H0, with three strong gravitational lens systems. We describe a blind analysis of both PG 1115+080 and HE 0435−1223 as well as an extension of our previous analysis of RXJ 1131−1231. For each lens, we combine new adaptive optics (AO) imaging from the Keck Telescope, obtained as part of the SHARP (S...
Citations
... Narrow line emission from quasars has been the main source of data in the past (Nierenberg et al. 2020 ) and this will continue to impro v e as larger data sets at higher resolution and precision are acquired with impro v ed adaptiv e optics and instruments such as Keck All-sky Precision Adaptive-optics (KAPA) (Wizinowich et al. 2022 ) and LIGER (Wright et al. 2019 ) currently under development at Keck. Furthermore, the launch of JWST has opened up the new exciting possibility to use flux ratios measured in the mid-infrared, where the source is typically smaller than the narrow line emission and thus more sensitive to low-mass perturbations. ...
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... Strong gravitational lensing (SL) has proven to be an important tool to learn about the Universe because of its sensitivity to the geometry of the Universe and the matter distribution therein, for example, by constraining cosmological parameters (Jullo et al. 2010;Collett et al. 2012;Cao et al. 2015;Linder 2016), testing gravity Koopmans et al. 2009;Collett et al. 2018), and measuring the mass distribution of intervening objects (Shu et al. 2008;Coe et al. 2012;Gomer & Williams 2020;Chen et al. 2022). In addition, SL can magnify distant galaxies and help us look into their properties in more detail (e.g., Marshall et al. 2007;Newton et al. 2011). ...
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... In our experiment, this can be retrieved by placing a narrowband filter in the idler arm, whose width is narrower than the resolution of the spectrometer, leading to the results in Fig. 2(a). This is akin to what is the standard in astronomical observations, where a distant star serves as a reference to obtain the point spread function of the imaging system [22]. Notice how the instrumental function in ghost imaging schemes is dictated not only by the optical components, but also by the degree of correlation between the two photons [23] An interferometric filter serves as our spectral object: as an example, a reconstructed profile appears in Fig. 2(b). ...
... For more details on the modelling problem for the function J, see Section 4.6 of [53]. The posterior distribution of these lenses (namely RXJ1131-1231 [31,54], PG1115+080 [55], B1608+656 3 [56,57], J1206+4332 [53], WFI2033-4723 [59], HE0435-1223 [55,58]) including the time delay distances and the angular diameter distances of the lenses can be found at H0LiCOW website 4 . The redshifts of both lenses and sources, time delay distances and angular diameter distances to lenses for systems are summarized in Table 2 of Wong et al. [34]. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/385194180792323-1468848857521_Q64/Vivien-Bonvin.jpg)
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... For more details on the modelling problem for the function J, see Section 4.6 of [53]. The posterior distribution of these lenses (namely RXJ1131-1231 [31,54], PG1115+080 [55], B1608+656 3 [56,57], J1206+4332 [53], WFI2033-4723 [59], HE0435-1223 [55,58]) including the time delay distances and the angular diameter distances of the lenses can be found at H0LiCOW website 4 . The redshifts of both lenses and sources, time delay distances and angular diameter distances to lenses for systems are summarized in Table 2 of Wong et al. [34]. ...
... Many of the interacting DM-DE models were invoked to try and explain the recent tensions in cosmology (for a review see ref. [78]). These tensions correspond to discrepancies between local measurements of observables [79,80] and modeldependent results from CMB data analysis at early times [81][82][83]. One of the most severe of these tensions is the Hubble tension which corresponds to a disagreement, at the 5σ level, between local measurements from the SH0ES collaboration [84] using Cepheid-calibrated supernovae and early time predictions using the CMB data from the Planck collaboration [85]. ...
