19 research outputs found
Structure and Color Gradients of Ultra-diffuse Galaxies in Distant Massive Galaxy Clusters
We have measured structural parameters and radial color profiles of 108
ultra-diffuse galaxies (UDGs), carefully selected from six distant massive
galaxy clusters in the Hubble Frontier Fields (HFF) in redshift range from
0.308 to 0.545. Our best-fitting GALFIT models show that the HFF UDGs have a
median S\'ersic index of 1.09, which is close to 0.86 for local UDGs in the
Coma cluster. The median axis-ratio value is 0.68 for HFF UDGs and 0.74 for
Coma UDGs, respectively. The structural similarity between HFF and Coma UDGs
suggests that they are the same kind of galaxies seen at different times and
the structures of UDGs do not change at least for several billion years. By
checking the distribution of HFF UDGs in the rest-frame and
diagrams, we find a large fraction of them are star-forming. Furthermore, a
majority of HFF UDGs show small color gradients within
\,1\,*\, region, the fluctuation of the median radial color profile
of HFF UDGs is smaller than 0.1\,mag, which is compatible to Coma UDGs. Our
results indicate that cluster UDGs may fade or quench in a self-similar way,
irrespective of the radial distance, in less than 4 Gyrs.Comment: 17 pages, 8 figures, accepted for publication in Ap
ClusterFormer: Clustering As A Universal Visual Learner
This paper presents CLUSTERFORMER, a universal vision model that is based on
the CLUSTERing paradigm with TransFORMER. It comprises two novel designs: 1.
recurrent cross-attention clustering, which reformulates the cross-attention
mechanism in Transformer and enables recursive updates of cluster centers to
facilitate strong representation learning; and 2. feature dispatching, which
uses the updated cluster centers to redistribute image features through
similarity-based metrics, resulting in a transparent pipeline. This elegant
design streamlines an explainable and transferable workflow, capable of
tackling heterogeneous vision tasks (i.e., image classification, object
detection, and image segmentation) with varying levels of clustering
granularity (i.e., image-, box-, and pixel-level). Empirical results
demonstrate that CLUSTERFORMER outperforms various well-known specialized
architectures, achieving 83.41% top-1 acc. over ImageNet-1K for image
classification, 54.2% and 47.0% mAP over MS COCO for object detection and
instance segmentation, 52.4% mIoU over ADE20K for semantic segmentation, and
55.8% PQ over COCO Panoptic for panoptic segmentation. For its efficacy, we
hope our work can catalyze a paradigm shift in universal models in computer
vision
CryptoMask : Privacy-preserving Face Recognition
Face recognition is a widely-used technique for identification or
verification, where a verifier checks whether a face image matches anyone
stored in a database. However, in scenarios where the database is held by a
third party, such as a cloud server, both parties are concerned about data
privacy. To address this concern, we propose CryptoMask, a privacy-preserving
face recognition system that employs homomorphic encryption (HE) and secure
multi-party computation (MPC). We design a new encoding strategy that leverages
HE properties to reduce communication costs and enable efficient similarity
checks between face images, without expensive homomorphic rotation.
Additionally, CryptoMask leaks less information than existing state-of-the-art
approaches. CryptoMask only reveals whether there is an image matching the
query or not, whereas existing approaches additionally leak sensitive
intermediate distance information. We conduct extensive experiments that
demonstrate CryptoMask's superior performance in terms of computation and
communication. For a database with 100 million 512-dimensional face vectors,
CryptoMask offers and speed-ups
in terms of computation and communication, respectively.Comment: 18 pages,3 figures, accepted by ICICS202
Revisiting Galaxy Evolution in Morphology in the COSMOS field (COSMOS-ReGEM):I. Merging Galaxies
We revisit the evolution of galaxy morphology in the COSMOS field over the
redshift range , using a large and complete sample of 33,605
galaxies with a stellar mass of log(/M with
significantly improved redshifts and comprehensive non-parametric morphological
parameters. Our sample has 13,881 () galaxies with reliable
spectroscopic redshifts and has more accurate photometric redshifts with a
. This paper is the first in a series that
investigates merging galaxies and their properties. We identify 3,594 major
merging galaxies through visual inspection and find 1,737 massive galaxy pairs
with log(/M). Among the family of non-parametric
morphological parameters including , , , , , , and , we find that the outer asymmetry parameter
and the second-order momentum parameter are the best tracers of
merging features than other combinations. Hence, we propose a criterion for
selecting candidates of violently star-forming mergers: at at .
Furthermore, we show that both the visual merger sample and the pair sample
exhibit a similar evolution in the merger rate at , with for the visual merger sample and for the pair sample. The visual merger sample has a
specific star formation rate that is about 0.16\,dex higher than that of
non-merger galaxies, whereas no significant star formation excess is observed
in the pair sample. This suggests that the effects of mergers on star formation
differ at different merger stages.Comment: 21 pages, 12 figures; accepted for publication in Ap
HybPSF: Hybrid PSF reconstruction for the observed JWST NIRCam image
The James Webb Space Telescope (JWST) ushers in a new era of astronomical
observation and discovery, offering unprecedented precision in a variety of
measurements such as photometry, astrometry, morphology, and shear measurement.
Accurate point spread function (PSF) models are crucial for many of these
measurements. In this paper, we introduce a hybrid PSF construction method
called HybPSF for JWST NIRCam imaging data. HybPSF combines the WebbPSF
software, which simulates the PSF for JWST, with observed data to produce more
accurate and reliable PSF models. We apply this method to the SMACS J0723
imaging data and construct supplementary structures from residuals obtained by
subtracting the WebbPSF PSF model from the data. Our results show that HybPSF
significantly reduces discrepancies between the PSF model and the data compared
to WebbPSF. Specifically, the PSF shape parameter ellipticity and size
comparisons indicate that HybPSF improves precision by a factor of
approximately 10 for \$R^2\$ and \$50\%\$ for \$e\$. This improvement has
important implications for astronomical measurements using JWST NIRCam imaging
data
Divergent Syntheses of 2‑Aminonicotinonitriles and Pyrazolines by Copper-Catalyzed Cyclization of Oxime Ester
Copper-catalyzed
cyclization of an oxime ester toward divergent
heterocycle synthesis is reported. Oxime ester serves as an enamine
precursor to cyclize with malononitrile and aldehydes for access to
2-aminonicotinonitriles in a one-pot reaction, while cyclizing with <i>N</i>-sulfonylimines leads to synthesis of pyrazolines
Color profiles of 108 UDGs identified in HFF fields
Multi-band surface brightness profiles of 108 UDGs identified in HFF fields. Details about each diagram are listed below.
Panels\,(1) to (3) show the F814W band cutout-images of the UDG, the best-fitting GALFIT model and residual image. The bar at top-right of panel\,(2) represents 1.5\,kpc assuming the cluster redshift.
Panels\,(4) to (6) show PSF-matched images in F606W, F814W and F160W bands.
In panels\,(7) to (9), we mask neighboring sources classified by `Noisechisel' and overplot our elliptical annuli used in surface brightness analysis.
Panel\,(10) presents three-band surface brightness profiles of each UDG,
x-axis of colorful points correspond to the out-radius of elliptical annuli.
In panel\,(11), we convert observed color profiles into rest-frame U\,-\,V and V\,-\,I profiles.
F814W and F160W surface brightness profiles in panel\,(10) and rest-frame V\,-\,I profiles in panel\,(11) are shifted a bit to the right.
Finally, the colors of the UDG from inside to outside are shown in the UVI diagram in panel\,(12).
Please note that for UDGs which do not have F160W observations will not have panels (6),(9),(12)
GL-RG: Global-Local Representation Granularity for Video Captioning
Video captioning is a challenging task as it needs to accurately transform
visual understanding into natural language description. To date,
state-of-the-art methods inadequately model global-local representation across
video frames for caption generation, leaving plenty of room for improvement. In
this work, we approach the video captioning task from a new perspective and
propose a GL-RG framework for video captioning, namely a
\textbf{G}lobal-\textbf{L}ocal \textbf{R}epresentation \textbf{G}ranularity.
Our GL-RG demonstrates three advantages over the prior efforts: 1) we
explicitly exploit extensive visual representations from different video ranges
to improve linguistic expression; 2) we devise a novel global-local encoder to
produce rich semantic vocabulary to obtain a descriptive granularity of video
contents across frames; 3) we develop an incremental training strategy which
organizes model learning in an incremental fashion to incur an optimal
captioning behavior. Experimental results on the challenging MSR-VTT and MSVD
datasets show that our DL-RG outperforms recent state-of-the-art methods by a
significant margin. Code is available at \url{https://github.com/ylqi/GL-RG}.Comment: Accepted to IJCAI 202