ORCID Profile
0000-0001-8917-2148
Current Organisation
Kavli Institute for the Physics and Mathematics of the Universe
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Publisher: American Astronomical Society
Date: 10-2022
Abstract: We present the first rest-frame optical size–luminosity relation of galaxies at z 7, using the NIRCam imaging data obtained by the GLASS James Webb Space Telescope Early Release Science (GLASS-JWST-ERS) program, providing the deepest extragalactic data of the ERS c aign. Our s le consists of 19 photometrically selected bright galaxies with m F444W ≤ 27.8 at 7 z 9 and m F444W 28.2 at z ∼ 9−15. We measure the size of the galaxies in five bands, from rest-frame optical (∼4800 Å) to the UV (∼1600 Å) based on the Sérsic model, and analyse the size–luminosity relation as a function of wavelength. Remarkably, the data quality of the NIRCam imaging is sufficient to probe the half-light radius r e down to ∼100 pc at z 7. Given the limited s le size and magnitude range, we first fix the slope to that observed for larger s les in rest-frame UV using Hubble Space Telescope s les. The median size r 0 at the reference luminosity M = −21 decreases slightly from rest-frame optical (600 ± 80 pc) to UV (450 ± 130 pc). We then refit the size–luminosity relation allowing the slope to vary. The slope is consistent with β ∼ 0.2 for all bands except F150W, where we find a marginally steeper slope of β = 0.53 ± 0.15. The steep UV slope is mainly driven by the smallest and faintest galaxies. If confirmed by larger s les, it implies that the UV size–luminosity relation breaks toward the faint end, as suggested by lensing studies.
Publisher: Oxford University Press (OUP)
Date: 22-03-2023
Abstract: How does the host galaxy morphology influence a central quasar or vice versa? We address this question by measuring the asymmetries of 2424 SDSS quasar hosts at 0.2 & z & 0.8 using broad-band (grizy) images from the Hyper Suprime-Cam Subaru Strategic Program. Control galaxies (without quasars) are selected by matching the redshifts and stellar masses of the quasar hosts. A two-step pipeline is run to decompose the PSF and Sérsic components and then measure asymmetry indices (ACAS, Aouter, and Ashape) of each quasar host and control galaxy. We find a mild correlation between host asymmetry and AGN bolometric luminosity (Lbol) for the full s le (spearman correlation of 0.37) while a stronger trend is evident at the highest luminosities (Lbol & 45). This then manifests itself into quasar hosts being more asymmetric, on average, when they harbour a more massive and highly accreting black hole. The merger fraction also positively correlates with Lbol and reaches up to 35 per cent for the most luminous. Compared to control galaxies, quasar hosts are marginally more asymmetric (excess of 0.017 in median at 9.4σ level) and the merger fractions are similar ($\\sim 16.5~{{\\ \\rm per\\ cent}}$). We quantify the dependence of asymmetry on optical band that demonstrates that mergers are more likely to be identified with the bluer bands and the correlation between Lbol and asymmetry is also stronger in such bands. We stress that the band dependence, indicative of a changing stellar population, is an important factor in considering the influence of mergers on AGN activity.
Publisher: Springer Science and Business Media LLC
Date: 28-06-2023
Publisher: Oxford University Press (OUP)
Date: 12-09-2019
Abstract: 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 (Strong-lensing High Angular Resolution Programme) AO effort, with Hubble Space Telescope (HST) imaging, velocity dispersion measurements, and a description of the line-of-sight mass distribution to build an accurate and precise lens mass model. This mass model is then combined with the COSMOGRAIL-measured time delays in these systems to determine H0. We do both an AO-only and an AO + HST analysis of the systems and find that AO and HST results are consistent. After unblinding, the AO-only analysis gives $H_{0}=82.8^{+9.4}_{-8.3}~\\rm km\\, s^{-1}\\, Mpc^{-1}$ for PG 1115+080, $H_{0}=70.1^{+5.3}_{-4.5}~\\rm km\\, s^{-1}\\, Mpc^{-1}$ for HE 0435−1223, and $H_{0}=77.0^{+4.0}_{-4.6}~\\rm km\\, s^{-1}\\, Mpc^{-1}$ for RXJ 1131−1231. The joint AO-only result for the three lenses is $H_{0}=75.6^{+3.2}_{-3.3}~\\rm km\\, s^{-1}\\, Mpc^{-1}$. The joint result of the AO + HST analysis for the three lenses is $H_{0}=76.8^{+2.6}_{-2.6}~\\rm km\\, s^{-1}\\, Mpc^{-1}$. All of these results assume a flat Λ cold dark matter cosmology with a uniform prior on Ωm in [0.05, 0.5] and H0 in [0, 150] $\\rm km\\, s^{-1}\\, Mpc^{-1}$. This work is a collaboration of the SHARP and H0LiCOW teams, and shows that AO data can be used as the high-resolution imaging component in lens-based measurements of H0. The full time-delay cosmography results from a total of six strongly lensed systems are presented in a companion paper.
Publisher: Oxford University Press (OUP)
Date: 08-2012
DOI: 10.1017/S1431927612012974
Abstract: Since the discovery of the piezoelectric character of bone, the suitability of some piezoelectric materials have been studied for bone repair they are thought to act like transducers converting the mechanical energy of skeletal deformation in electrical stimuli capable of controlling osteogenic growth. The mechanisms underlying this process are far from being understood and systematic studies at a local scale are required. Atomic force microscopy (AFM) is a unique way to observe phenomena at the nanoscale and liquid imaging provides a unique tool to assess biological phenomena at the nanoscale. So in this study, aiming at a better understanding of the role of piezoelectricity in the osteogenic growth, the interaction between a poled piezoelectric material, in this case poly (L-lactic) acid and an adhesion promoting protein, the fibronectin, and bone-like cells is evaluated by scanning probe microscopy and confocal laser scanning microscopy (CLSM).
Publisher: American Astronomical Society
Date: 04-2023
Abstract: The conditions under which galactic nuclear regions become active are largely unknown, although it has been hypothesized that secular processes related to galaxy morphology could play a significant role. We investigate this question using optical i -band images of 3096 SDSS quasars and galaxies at 0.3 z 0.6 from the Hyper Suprime-Cam Subaru Strategic Program, which possesses a unique combination of area, depth, and resolution, allowing the use of residual images, after removal of the quasar and smooth galaxy model, to investigate internal structural features. We employ a variational auto-encoder, which is a generative model that acts as a form of dimensionality reduction. We analyze the lower-dimensional latent space in search of features that correlate with nuclear activity. We find that the latent space does separate images based on the presence of nuclear activity, which appears to be associated with more pronounced components (i.e., arcs, rings, and bars) as compared to a matched control s le of inactive galaxies. These results suggest the importance of secular processes and possibly mergers (by their remnant features) in activating or sustaining black hole growth. Our study highlights the breadth of information available in ground-based imaging taken under optimal seeing conditions and having an accurate characterization of the point-spread function (PSF), thus demonstrating future science to come from the Rubin Observatory.
Publisher: AIP Publishing
Date: 09-07-2012
DOI: 10.1063/1.4729619
Abstract: This paper describes the decay kinetics of electrically induced polarization of poly(L-lactic) acid (PLLA) via piezoresponse force microscopy. Two crystalline forms of PLLA (α and α′) were electrically poled at different temperatures (room and above glass transition). Poling at temperatures above glass transition allowed obtaining polarization stable up to 10 days for both forms. This period is enough to trigger and maintain proteins adhesion and cells proliferation, if PLLA is used as a platform for tissue growth. When poled at room temperature, both structures lose polarization after a short time (minutes to hours) being polarization in α PLLA stable for longer time.
Location: Japan
Location: United States of America
No related grants have been discovered for Xuheng Ding.