Recent Developments on the H_(I)Gas of Low-Redshift Galaxies Seen by the 21 cm Emission Lines

As a major interstellar medium,the atomic neutral hydrogen(H_(I))plays an important role in the galaxy evolution.It provides the ingredient for star formation,and sensitively traces the internal processes and external perturbations influencing the galaxy.With the beginning of many new radio telescopes and surveys,H_(I)may make a more significant contribution to the understanding of galaxies in the near future.This review discusses the major development of the 21 cm emission-line H_(I)observations and studies in the past few years,including its scaling relations with other galaxy properties,its kinematics and structures,its role in environmental studies,and its constraints on hydrodynamical simulations.The local-Universe H_(I)scaling relations of stellar-massselected samples extend smoothly to 10^(9)M⊙stellar mass,with a tentative evolution to the redshift of∼0.1.The development of measurement techniques enables better estimations of H_(I)non-circular motion,dispersion,and thickness,and new observations revealed extended or extra-planar H_(I)structures,both helpfully constraining the gas accretion,stellar feedback,and star formation processes of galaxy evolution models.H_(I)is very useful for tracing the satellite evolution in dense environments,the studies of which would benefit from ongoing blind H_(I)surveys.Though simulations still cannot fully reproduce H_(I)gas properties,they help to understand the role of possible factors in regulating H_(I)properties.

The Coevolutionary Relationship of Technology, Market and Government Regulation in Telecommunications

The telecommunications industry has been undergoing tremendous technological changes, and owning to continuous technological advancement, it has maintained sustained prosperity and development. In this paper, the interplay between technology, market and government in telecommunications is discussed briefly, and then we introduce technology and government into the traditional SCP(Structure – Conduct – Performance) paradigm to develop an industry analysis framework called TGM(SCP)(Technology – Government – Market(Structure – Conduct – Performance)). Based on this framework, we present the spiral coevolution model which elaborates on the interaction mechanism of technological innovation with government regulation and market dynamics from the perspective of industry evolution. Our study indicates that the development of the telecommunications industry is the result of the coevolution of technology, government regulation and market forces, and among the three actors, technology is the fundamental driving force. Relative to the "invisible hand"(market) and "visible hand"(government), we conceptualize technology as the "third hand", which fundamentally drives the development of telecommunications industry in coordination with the other two hands. We also provide several policy implications regarding these findings.

Mapping HⅠ in the NGC 4636 Galaxy Group with FAST

This paper presents data from a 21 cm H I emission drift scan observation of a field partially covering the NGC 4636 galaxy group with the Five-hundred meter Aperture Radio Telescope(FAST). We construct a pipeline to reduce the data, and use So Fi A for source finding. When not contaminated by Radio Frequency Interference(RFI), the FAST observations are capable of detecting all of the galaxies previously detected by the Arecibo Legacy Fast ALFA(ALFALFA) survey in the same region. Comparing to ALFALFA for the detections in common, the FAST data show consistent integrated spectra when the H I disks are spatially unresolved, and capture more flux when the H I disks are resolved. The FAST data further reveal 10 new detections in the region mutually covered with ALFALFA, and 18 new detections beyond the footprint of ALFALFA. All of the new detections have the matching optical counterparts. For the member galaxies of the NGC 4636 group, the detection limit of FAST is deeper by 0.4 dex in H I mass than that of the ALFALFA data. After correcting for the incompleteness caused by RFI contamination, we show that the H I detection rate of galaxies rises steeply with radius out to the virial radius of the group, and flattens beyond that. We also examine four spatially resolved galaxy systems with potential tidal interaction features in detail. Considering that the data have been taken during the“shared-risk” period before a major source of local RFI was eliminated, the results highlight the power of FAST in detecting extragalactic H I.