This study investigates the relationship between the detection rates of MgⅡabsorption lines and the asymmetries of[OⅢ]emission lines.We first select 21,364 quasars from the Sloan Digital Sky Survey DR12Q exhibiting ...This study investigates the relationship between the detection rates of MgⅡabsorption lines and the asymmetries of[OⅢ]emission lines.We first select 21,364 quasars from the Sloan Digital Sky Survey DR12Q exhibiting prominent[OⅢ]emission lines,of which 351 quasars have Category 1 MgⅡabsorption lines(4365≤υ_(r)≤10,000 km s^(-)1)and 518 quasars have Category 2 MgⅡabsorption lines(610≤υ_(r)≤4365 km s-1).Subsequently,we quantify the asymmetries of[OⅢ]emission lines using the velocity offsetδv,and find that the detection rates of Category 1 MgⅡabsorption lines(predominantly intervening absorbers)show no correlation with the blueshifted asymmetries of[OⅢ]emission lines,whereas the detection rates of Category 2 MgⅡabsorption lines(primarily outflow and intervening absorbers)increase with risingδ_(v).Finally,we discuss the results from two perspectives:quasar evolutionary stages and acceleration mechanisms driven by radiation pressure.展开更多
Gamma-ray bursts (GRBs) are the most intense transient gamma-ray events in the sky; this, together with the strong evidence (the isotropic and inhomogeneous distribution of GRBs detected by BASTE) that they are locat...Gamma-ray bursts (GRBs) are the most intense transient gamma-ray events in the sky; this, together with the strong evidence (the isotropic and inhomogeneous distribution of GRBs detected by BASTE) that they are located at cosmological distances, makes them the most energetic events ever known. For example, the observed radiation energies of some GRBs are equivalent to the total convertion into radiation of the mass energy of more than one solar mass. This is thousand times stronger than the energy of a supernova explosion. Some unconventional energy mechanism and extremely high conversion efficiency for these mysterious events are required. The discovery of host galaxies and association with supernovae at cosmological distances by the recently launched satellite of BeppoSAX and ground based radio and optical telescopes in GRB afterglow provides further support to the cosmological origin of GRBs and put strong constraints on their central engine. It is the aim of this article to review the possible central engines, energy mechanisms, dynamical and spectral evolution of GRBs, especially focusing on the afterglows in multi-wavebands.展开更多
We present large-scale(2°×2°)observations toward the molecular cloud M120.1+3.0,using ^(12)CO,^(13)CO and C^(18)O(J=1-0)data from the Purple Mountain Observatory 13.7 m millimeter telescope.The distance...We present large-scale(2°×2°)observations toward the molecular cloud M120.1+3.0,using ^(12)CO,^(13)CO and C^(18)O(J=1-0)data from the Purple Mountain Observatory 13.7 m millimeter telescope.The distance of the cloud is measured to be~1.1 kpc.Using the ^(13)CO data,we identify a main filament F1 and two sub-filaments F2 and F3 in the cloud,which together show a"hub-filament"structure.Filaments F1 and F2 are thermally supercritical.Furthermore,F1 displays clear localized systematic motions in the ^(13)CO position-velocity diagram,which could be explained by accretion along the filament.The mean estimated accretion rate is~132M_(⊙)Myr^(-1).Approximately 150 ^(13)CO clumps are identified in the cloud,of which 39 are gravitationally bound.Most of these virialized clumps are well distributed along the supercritical filaments F1 and F2.Based on the complementary infrared and optical data,we identify~186 young stellar objects in the observed area and extract five clusters within the dense ridge of F1.The calculated star formation rate(SFR)surface densities(∑_(SFR))in the clusters range from 1.4 to 2.5 M_(⊙)Myr^(-1)pc^(-2),with a mean value of~2.0M_(⊙)Myr^(-1)pc^(-2).We therefore regard them as mini-starburst cluster candidates.The comparison between ∑_(SFR) and column density N_(gas) along the skeleton of F1 suggests that star formation is closely related to the dense gas in the cloud.Along the main filament F1,five bipolar outflows are also found.All these results indicate intense star-forming activities in the M120.1+3.0 molecular cloud.展开更多
基金supported by the Scientific Research Project of Guangxi Minzu University(2023KJQD07)Guangxi Natural Science Foundation(2025GXNSFBA069287)+2 种基金the Guangxi Natural Science Foundation(2024GXNSFDA010069,2019GXNSFFA245008)the National Natural Science Foundation of China(12073007)the Scientific Research Project of Guangxi University for Nationalities(2018KJQD01)。
文摘This study investigates the relationship between the detection rates of MgⅡabsorption lines and the asymmetries of[OⅢ]emission lines.We first select 21,364 quasars from the Sloan Digital Sky Survey DR12Q exhibiting prominent[OⅢ]emission lines,of which 351 quasars have Category 1 MgⅡabsorption lines(4365≤υ_(r)≤10,000 km s^(-)1)and 518 quasars have Category 2 MgⅡabsorption lines(610≤υ_(r)≤4365 km s-1).Subsequently,we quantify the asymmetries of[OⅢ]emission lines using the velocity offsetδv,and find that the detection rates of Category 1 MgⅡabsorption lines(predominantly intervening absorbers)show no correlation with the blueshifted asymmetries of[OⅢ]emission lines,whereas the detection rates of Category 2 MgⅡabsorption lines(primarily outflow and intervening absorbers)increase with risingδ_(v).Finally,we discuss the results from two perspectives:quasar evolutionary stages and acceleration mechanisms driven by radiation pressure.
基金a RGC grant of the Hong Kong Government and the National Natural Science Foundation of China.
文摘Gamma-ray bursts (GRBs) are the most intense transient gamma-ray events in the sky; this, together with the strong evidence (the isotropic and inhomogeneous distribution of GRBs detected by BASTE) that they are located at cosmological distances, makes them the most energetic events ever known. For example, the observed radiation energies of some GRBs are equivalent to the total convertion into radiation of the mass energy of more than one solar mass. This is thousand times stronger than the energy of a supernova explosion. Some unconventional energy mechanism and extremely high conversion efficiency for these mysterious events are required. The discovery of host galaxies and association with supernovae at cosmological distances by the recently launched satellite of BeppoSAX and ground based radio and optical telescopes in GRB afterglow provides further support to the cosmological origin of GRBs and put strong constraints on their central engine. It is the aim of this article to review the possible central engines, energy mechanisms, dynamical and spectral evolution of GRBs, especially focusing on the afterglows in multi-wavebands.
基金supported by the National Key R&D Program of China(grant No.2017YFA0402702)the National Natural Science Foundation of China(NSFC,Grant Nos.12041305,12173090 and 12073079)+2 种基金the CAS International Cooperation Program(grant No.114332KYSB20190009)sponsored by the National Key R&D Program of China with grant 2017YFA0402701the CAS Key Research Program of Frontier Sciences with grant QYZDJ-SSW-SLH047。
文摘We present large-scale(2°×2°)observations toward the molecular cloud M120.1+3.0,using ^(12)CO,^(13)CO and C^(18)O(J=1-0)data from the Purple Mountain Observatory 13.7 m millimeter telescope.The distance of the cloud is measured to be~1.1 kpc.Using the ^(13)CO data,we identify a main filament F1 and two sub-filaments F2 and F3 in the cloud,which together show a"hub-filament"structure.Filaments F1 and F2 are thermally supercritical.Furthermore,F1 displays clear localized systematic motions in the ^(13)CO position-velocity diagram,which could be explained by accretion along the filament.The mean estimated accretion rate is~132M_(⊙)Myr^(-1).Approximately 150 ^(13)CO clumps are identified in the cloud,of which 39 are gravitationally bound.Most of these virialized clumps are well distributed along the supercritical filaments F1 and F2.Based on the complementary infrared and optical data,we identify~186 young stellar objects in the observed area and extract five clusters within the dense ridge of F1.The calculated star formation rate(SFR)surface densities(∑_(SFR))in the clusters range from 1.4 to 2.5 M_(⊙)Myr^(-1)pc^(-2),with a mean value of~2.0M_(⊙)Myr^(-1)pc^(-2).We therefore regard them as mini-starburst cluster candidates.The comparison between ∑_(SFR) and column density N_(gas) along the skeleton of F1 suggests that star formation is closely related to the dense gas in the cloud.Along the main filament F1,five bipolar outflows are also found.All these results indicate intense star-forming activities in the M120.1+3.0 molecular cloud.
