Velocity offset between emission and absorption lines might be an effective indicator of dual core system

This paper presents a detection of significant velocity offset between emission and absorption lines for a dual core system in SDSS~J155708.82+273518.74 (= SDSS~J1557). The photometric image of SDSS~J1557 exhibits clear two cores with a projected separation of $\sim$2.2 arcseconds (4.9 kpc) determined by GALFIT. Based on the applications of the commonly accepted pPXF code with 636 theoretical SSP templates, the host galaxy contribution can be well determined. Then, the emission line features of SDSS~J1557 can be well measured after subtraction of host starlight. It is found that the velocity offset of emission lines with respect to absorption lines reaches $458 \pm 13$ km/s. According to the Baldwin-Phillips-Terlevich (BPT) diagram, SDSS J1557 is a composite galaxy. In addition, SDSS J1557 can well fit the $M_{\rm BH}-\sigma_{\ast}$ relation of bulges and the galaxy merger would not change this relation. Two reasonable models (say, AGN-driven outflow vs. dual core system) have been discussed to explain this velocity offset. The model of AGN-driven outflow fails to interpret the systematic redshift of emission lines and similar velocity offsets for various emission lines in SDSS~J1557. A significant velocity offset between emission and absorption lines might be an effective indicator of dual core system.Comment: 13 pages, 7 figures, accepted to be published in Ap

A Study on High-Speed Rail Pricing Strategy in the Context of Modes Competition

High-speed rail (HSR) has developed rapidly in China over the recent years, for the less pollution, faster speed, comfort, and safety. However, there is still an issue on how to improve the seat occupancy rates for some HSR lines. This research analyzes the pricing strategy for HSR in Wuhan-Guangzhou corridor based on the competition among different transport modes with the aim of improving occupancy rates. It starts with the theoretical analysis of relationship between market share and ticket fare, and then disaggregate choice models with nested structure based on stated preference (SP) data are established to obtain the market share of HSR under specific ticket fare. Finally, a pricing strategy is proposed to improve the occupancy rates for Wuhan-Guangzhou HSR. The results confirm that a pricing strategy with floating fare should be accepted to improve the profit of HSR; to be specific, the ticket fare should be set in lower level on weekdays and higher level on holidays