发表机构
Department of Astronomy, Tsinghua University; School of Physics and Laboratory of Zhongyuan Light, Zhengzhou University（清华大学天文系; 郑州大学物理学院与中原光实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过SDSS光学和UKIDSS近红外多波段图像分解，发现光学超薄星系在近红外仍保持薄盘，且其极端盘形态与低质量暗物质晕环境相关。
AI 中文摘要
我们研究了在光学图像中被识别为超薄的星系在近红外（NIR）是否仍然保持超薄，以及其极端盘形态与环境的关系。从一个近邻体积限制样本中，我们通过SDSS $r$ 波段图像的二维核球/盘分解选出210个超薄星系，要求盘成分的长短轴比 $a/b>9$。我们测量了从SDSS $griz$ 到UKIDSS $JHK$ 波段的盘形状。从光学到近红外，长轴和短轴尺度均减小，在 $K$ 波段达到 $r$ 波段值的 $\sim0.6$，但盘轴比几乎不变。因此，光学选中的超薄星系在近红外仍然保持超薄，这意味着近红外光追踪的老年恒星种群并未形成显著的厚盘。重新分析我们的样本和之前的超薄样本表明，先前报道的近红外增厚主要源于一维拟合中的星等和波段依赖偏差。我们进一步通过投影互相关、重建的局部超密度和大尺度结构分类，将它们的环境与匹配的对照样本进行比较。超薄星系在 $\sim0.1$--$1\,h^{-1}\,\mathrm{Mpc}$ 尺度上显示出较低的成团性，在 $1\,h^{-1}\,\mathrm{Mpc}$ 处超密度较低，但对大尺度结构类型没有明显的残余依赖。这些结果表明，超薄星系优先位于相对低质量的暗物质晕中的中央星系，这与高宿主晕自旋有助于构建和维持延展、垂直薄恒星盘的图景一致。
英文摘要
We investigate whether galaxies identified as superthin in optical images remain superthin in the near-infrared (NIR), and how their extreme disk morphology is related to environment. From a nearby volume-limited sample, we select 210 superthin galaxies using two-dimensional bulge/disk decomposition of SDSS $r$-band images, requiring the disk component to have a minor-to-major axis ratio $b/a<1/9$. We measure disk shapes from SDSS $griz$ to UKIDSS $JHK$ bands. Both the major- and minor-axis scales decrease from the optical to the NIR, reaching $\sim0.6$ of their $r$-band values in the $K$ band, but the disk axis ratio remains nearly unchanged. Thus, optically selected superthin galaxies remain superthin in the NIR, suggesting that any NIR-dominant thick component, if present, is not prominent enough to alter the fitted disk shape. Reanalysis of our sample and a previous superthin sample shows that earlier reported NIR thickening is mainly due to a magnitude- and band-dependent bias in one-dimensional fitting. We further compare their environments with matched control samples using projected cross-correlations, reconstructed local overdensities, and large-scale-structure classifications. Superthin galaxies show lower clustering on $\sim0.1$--$1\,h^{-1}\,\mathrm{Mpc}$ scales and lower overdensities at $1\,h^{-1}\,\mathrm{Mpc}$, but similar large-scale clustering and no clear residual dependence on large-scale-structure type. These results are consistent with a higher central-galaxy fraction and lower satellite fraction in the superthin sample, while the similar large-scale clustering points to comparable typical halo masses relative to the controls. This halo-occupation interpretation is qualitatively consistent with simulation-based scenarios in which high host-halo spin helps build extended thin disks, although the present data do not directly measure halo spin.
Comments22 pages, 23 figures, 1 table, accepted for publication in MNRAS
