SDSS IV MaNGA: Discovery of an $H_α$ blob associated with a dry galaxy pair -- ejected gas or a `dark' galaxy candidate?

Outlying H$α$ blobs in SDSS IV MaNGA

We have discovered a population of 29 outlying H$α$ emitters which appear like unresolved blobs in the DR14 data release of the SDSS IV MaNGA integral field unit survey. They do not have any underlying optical continuum emission in deep imaging from the DECam Legacy Survey or Beijing-Arizona Sky Survey. These blobs either lie away from the disc of the host galaxy in the MaNGA IFU and/or have velocities which are different from the velocity map of the host galaxy. Interestingly, all of them show photoionisation due to star formation. These galaxies have very high specific star formation rates c…

SDSS-IV MaNGA: the physical origin of off-galaxy H$α$ blobs in the local Universe

H$α$ blobs are off-galaxy emission-line regions with weak or no optical counterparts. They are mostly visible in H$α$ line, appearing as concentrated blobs. Such unusual objects have been rarely observed and studied, and their physical origin is still unclear. We have identified 13 H$α$ blobs in the public data of MaNGA survey, by visually inspecting both the optical images and the spatially resolved maps of H$α$ line for $\sim 4600$ galaxy systems. Among the 13 H$α$ blobs, 2 were reported in previously MaNGA-based studies and 11 are newly discovered. This sample, though still small in size, i…

SDSS-IV MaNGA: The Nature of an Off-galaxy H$α$ Blob -- A Multi-wavelength View of Offset Cooling in a Merging Galaxy Group

Galaxies in dense environments, such as groups and clusters, experience various processes by which galaxies gain and lose gas. Using data from the SDSS-IV MaNGA survey, we previously reported the discovery of a giant (6 -- 8 kpc in diameter) H$α$ blob, Totoro, about 8 kpc away from a pair of galaxies (Satsuki and Mei) residing in a galaxy group which is experiencing a group-group merger. Here, we combine interferometric $^{12}$CO(1--0) molecular gas data, new wide-field H$α$, $u$-band data, and published X-ray data to determine the origin of the blob. Several scenarios are discussed to account…

低质量星系中双极斑块作为隐藏AGN活动的证据

Bipolar blobs as evidence of hidden AGN activities in the low-mass galaxies

本研究在低质量星系MaNGA 9885-9102中发现隐藏黑洞证据，提出利用双极Hα斑块探测活动黑洞光回声的新方法，在传统BPT图失效的低金属丰度环境中有效。

SDSS-IV MaNGA: Cannibalism Caught in the Act -- on the Frequency of Occurrence of Multiple Cores in Brightest Cluster Galaxies

Although it is generally accepted that massive galaxies form in a two-phased fashion, beginning with a rapid mass buildup through intense starburst activities, followed by primarily dry mergers that mainly deposit stellar mass at outskirts, the late time stellar mass growth of brightest cluster galaxies (BCGs), the most massive galaxies in the universe, is still not well understood. Several independent measurements have indicated a slower mass growth rate than predictions from theoretical models. We attempt to resolve the discrepancy by measuring the frequency of BCGs with multiple-cores, whic…

干并合在塑造星系标度关系中的作用

The role of dry mergers in shaping the scaling relations of galaxies

本研究基于标量位力定理构建多重干并合简易理论，结合观测数据与Illustris-TNG、EAGLE数值模拟验证，发现该机制可解释星系标度关系的主要特征，精度与现代模拟相当且计算更高效。