arXiv subjects

Xiaolan Hou

Publications and source records attributed to Xiaolan Hou.

4 recordsLinked to original sources

arXiv2026

Environmental Dependence of Star Formation and Galaxy Colors around Abell 2029

Environmental processes drive galaxy evolution, with the impact varying significantly across different stellar masses. We present a comprehensive environmental analysis of the galaxies within a $10^\circ \times 10^\circ$ field around A2029, utilizing high-density spectroscopic data from the DESI and SDSS surveys. We investigate the quenched fraction ($f_Q$) and red fraction ($f_{red}$) as functions of local surface density ($\log_{10} \Sigma_5$) across three stellar mass intervals (low-mass: $9.5 \le \log M_\star/M_\odot < 10.0$; medium-mass: $10.0 \le \log M_\star/M_\odot < 10.5$; high-mass: $\log M_\star/M_\odot \geq 10.5$ ). Our results show that, for galaxies of all masses, both star formation activity and galaxy color are strongly correlated with the local density. Although the environmental dependence of both the quenched and red fractions is somewhat weaker in low-mass galaxies than in their high-mass counterparts, the variations remain significant. This suggests that galaxy colors, even for low-mass systems, can serve as effective tracers of large-scale structure.

astro-ph.GA↗

arXiv2026

The dual effect of group-scale environments on galaxy quenching during cluster infall: pre-processing and protection

Context. It is well established that the cluster environment effectively quenches star formation in member galaxies. Amis. We aim to explore how the accretion path of infalling galaxies influences the cluster-driven quenching process. Methods. We compiled a large spectroscopic galaxy sample around 25 low-redshift, X-ray luminous massive clusters. We identified cluster substructures using the Blooming Tree algorithm and distinguished between galaxies accreted as part of group-scale structures and those accreted in isolation. The infall process was quantified using an infall proxy, $d_{\rm R}$, defined in the $R$--$V$ diagram. Results. Along the infall process, the quiescent fraction remains approximately constant at the outskirts and then increases steadily toward cluster center, with a transition occurring around $d_{\rm R}\sim 2.5$. We find that group-associated galaxies follow a distinct quenching track compared to isolated galaxies, indicating a dual effect of group-scale environments. At the early infall stages, group galaxies exhibit a higher quiescent fraction, consistent with ``pre-processing'' in group-scale halos. However, after entering the cluster environment, the rise in their quiescent fraction is delayed to smaller $d_{\rm R}$ compared to isolated galaxies. This suggests a phenomenological ``protection'' effect, in which group-scale halos buffer member galaxies against rapid cluster-driven quenching. Conclusions. We conclude that group-scale environments affect quenching in two ways: via pre-processing prior to cluster infall, and through a subsequent protection effect within the cluster environment.

astro-ph.GA↗

arXiv2026

The Optical Properties of Host Galaxies of Radio Sources in the Coma Cluster

We present a comprehensive study of host galaxies of radio sources within the 1.35$R_{200}$ of the Coma cluster by combining deep 144MHz observations from the LOFAR Two-Metre Sky Survey (LoTSS-DR2) with optical spectroscopy and photometry from DESI and SDSS. We identify 79 spectroscopically confirmed cluster members with reliable radio emission and classify them into compact, extended, and tailed subsamples according to their radio morphologies. By combining their radio and optical properties, we find compact radio sources are predominantly associated with massive, quiescent galaxies driven by AGN activity, while tailed sources are largely hosted by star-forming galaxies, tracing ongoing ram pressure stripping (RPS). Using phase-space analysis and a projected infall time proxy ($d_R$), we find that extended sources are preferentially located in the cluster outskirts ($d_R > 1$), while tailed sources are concentrated in the intermediate infall region ($0.4 < d_R < 1.0$), highlighting the influence of the dense intracluster medium.

astro-ph.GA↗

arXiv2022

Hierarchical Clustering in Astronomy

Hierarchical clustering is a common algorithm in data analysis. It is unique among many clustering algorithms in that it draws dendrograms based on the distance of data under a certain metric, and group them. It is widely used in all areas of astronomical research, covering various scales from asteroids and molecular clouds, to galaxies and galaxy cluster. This paper systematically reviews the history and current status of the development of hierarchical clustering methods in various branches of astronomy. These applications can be grouped into two broad categories, one revealing the intrinsic hierarchical structure of celestial systems and the other classifying large samples of celestial objects automatically. By reviewing these applications, we can clarify the conditions and limitations of the hierarchical clustering algorithm, and make more reasonable and reliable astronomical discoveries.

astro-ph.IM↗