arXiv subjects

Limeng Deng

Publications and source records attributed to Limeng Deng.

5 recordsLinked to original sources

arXiv2026

Discovery of a Strong-lens Galaxy Pair with the Smallest Projected Separation

We present the spectroscopic confirmation and lens modeling of HSC~J0233$-$0205, a strong-lensing system produced by a close pair of elliptical galaxies at $z_d=0.790\pm0.022$ that lenses a multi-component background source at $z_s=2.160\pm0.002$. The two deflectors are separated by only $0\arcsec.481\pm0\arcsec.004$ ($3.596\pm0.046$ kpc), making this system a compact galaxy-pair lens at relatively high redshift. Joint five-band HSC lens modeling requires two mass components, with Einstein radii of $0\arcsec.774\pm0\arcsec.011$ and $0\arcsec.767\pm0\arcsec.014$, and yields a circularized Einstein radius of $\theta_{\rm E}=1\arcsec.549\pm0\arcsec.018$ for the overall system. The lensed source is reconstructed with three components: two extended components separated by $0\arcsec.462\pm0\arcsec.013$ ($3.830\pm0.108$ kpc), together with a compact component nearly aligned with one of them. Integrating the lensing convergence map within the critical curve gives a projected mass of $M_{\rm lensing,crit}=(9.626\pm0.010)\times10^{11}M_\odot$. Combining this with the stellar mass inferred from SED fitting, $M_{\ast,{\rm crit}}=(1.570\pm0.240)\times10^{11}M_\odot$, we obtain a projected dark-matter fraction within the critical curve of $f_{\rm dm}=83.7\pm2.5\%$. Within the $z$-band effective radii of the two deflectors, the corresponding dark-matter fractions are $82.1\pm4.5\%$ and $65.7\pm6.7\%$, respectively. HSC~J0233$-$0205 is therefore a compact, high-redshift galaxy-pair lens. Future high-resolution imaging and spatially resolved spectroscopy will enable detailed tests of merger signatures, the redistribution of stellar and dark matter, and possible light--mass offsets in the lens plane.

astro-ph.GA↗

arXiv2026

Group Pre-processing in J1611+4026: Minor Rejuvenation of a Massive ETG fueled by Interaction-driven Gas Transfer

Interactions within galaxy groups are fundamental drivers of galactic evolution, and establishing a direct observational link between the dynamical processes of satellite galaxies and the rejuvenation of massive host galaxies remains challenging. We present a multi-wavelength work of J1611+4026, a unique triple system characterised by a massive early-type host galaxy, Component C and two gas-rich companions, Components A and B, which are currently undergoing a major merger in its near environment. Utilising deep optical imaging from DESI-LS and spectroscopic data from DESI and P200, we employ 2D morphological decomposition using \textsc{GALIGHT} alongside joint spectrophotometric synthesis modelling with \textsc{BAGPIPES} and \textsc{CIGALE} to deconstruct the structural properties and star formation histories of the member galaxies. Crucially, we identify an asymmetric tidal tail extending $\sim$15.15 kpc from Component A, confirming the ongoing interaction between the companions. Although Component C appears quiescent in both morphology and spectroscopy, we reveal a subtle robust signal of ``minor rejuvenation'', characterised by significant internal dust extinction of $E(B-V) \sim 0.53$ and a UV excess. The reconstructed star formation history indicates a recent ($\sim$100 Myr) starburst that contributes a negligible fraction to the total stellar mass ($f_{\rm burst} < 0.1$ per cent). We propose that this activity is fueled by the accretion of metal-enriched gas stripped from the interacting companions. These results strongly suggest group pre-processing, where interactions between satellite galaxies drive low-level star formation in the massive host through gas transfer, providing a quantitative benchmark for interaction-driven evolution in dense environments.

astro-ph.GA↗

arXiv2025

Discovery of a Low-mass Strong-lens System in SMACS J0723.3-7327

We report the discovery of an intriguing, low-mass galaxy-scale strong-lens system in the SMACS J0723.3-7327 galaxy cluster. By modeling James Webb Space Telescope imaging and Very Large Telescope Multi-Unit Spectroscopic Explorer spectroscopic data, we find that the lens is cluster member galaxy at $z=0.397$ with an Einstein radius of $0^{\prime \prime}.424$ $\pm$ $0^{\prime \prime}.012$, stellar mass of $M_* = (3.3 \pm 0.8) \times 10^{10} M_\odot$, half-light radius of $\sim 1$ kpc, and central stellar velocity dispersion of $140 \pm 6$ km s$^{-1}$. This lens galaxy is one of the few strong lens galaxies known to date that have stellar mass as low as $M_* \sim 10^{10.5} M_\odot$, offering an exceptional opportunity to peek into the population of low-mass galaxies that has largely remained unexplored in the context of strong-lensing studies. This strong lens system can also assist in assessing the systematic uncertainty in the lens modeling of cluster member galaxies.

astro-ph.GA↗

arXiv2025

Discovery of 19 strongly-lensed quasars, dual and projected quasars in DESI-LS

We report the follow-up spectroscopic confirmation of two lensed quasars, six dual quasars, and eleven projected quasars that were previously identified as lensed-quasar candidates in \cite{He2023}. The spectroscopic data were obtained from two different sources: the P200/DBSP in California and publicly available datasets, including SDSS and DESI-EDR. The two lensed quasars (both pairs) have the following properties: $\theta_E$ = 1.208'', $z_s$ = 3.105; $\theta_E$ = 0.749, $z_s$ = 2.395. The six dual quasars have redshifts ranging from 0.58 to 3.28 and projected separations ranging from 15.44 to 22.54 kpc, with a mean separation of 17.95 kpc. The eleven projected quasars have projected separations ranging from 10.96 to 39.07 kpc, with a mean separation of 22.64 kpc. Additionally, there are three likely lensed quasars that cannot be definitively confirmed, contributed by two reasons. Firstly, their image separations (0.83'', 0.98'', and 0.93'') are small compared to the seeing conditions during our observations (around 1.2''). Secondly, no high SNR lensing galaxy can be detected in the Legacy Survey Imaging. Better spectroscopy and (or) imaging are needed to confirm their lensing nature.

astro-ph.GA↗

arXiv2024

Using Convolutional Neural Networks to Search for Strongly Lensed Quasars in KiDS DR5

Gravitationally strongly lensed quasars (SL-QSO) offer invaluable insights into cosmological and astrophysical phenomena. With the data from ongoing and next-generation surveys, thousands of SL-QSO systems can be discovered expectedly, leading to unprecedented opportunities. However, the challenge lies in identifying SL-QSO from enormous datasets with high recall and purity in an automated and efficient manner. Hence, we developed a program based on a Convolutional Neural Network (CNN) for finding SL-QSO from large-scale surveys and applied it to the Kilo-degree Survey Data Release 5 (KiDS DR5). Our approach involves three key stages: firstly, we pre-selected ten million bright objects (with $r$-band $\tt{MAG\_AUTO} < 22$), excluding stars from the dataset; secondly, we established realistic training and test sets to train and fine-tune the CNN, resulting in the identification of 4195 machine candidates, and the false positive rate (FPR) of $\sim$1/2000 and recall of 0.8125 evaluated by using the real test set containing 16 confirmed lensed quasars; thirdly, human inspections were performed for further selections, and then 272 SL-QSO candidates were eventually found in total, including 16 high-score, 118 median-score, and 138 lower-score candidates, separately. Removing the systems already confirmed or identified in other papers, we end up with 229 SL-QSO candidates, including 7 high-score, 95 median-score, and 127 lower-score candidates, and the corresponding catalog is publicly available online. We have also included an excellent quad candidate in the appendix, discovered serendipitously during the fine-tuning process of the CNN.

astro-ph.GA↗