八十年代中,一些西方国家的电视台曾播放过一部“解剖外星人”的纪录片。据说该片是美国军方在六十年代拍摄的,密级AAA,杜鲁门总统曾亲临解剖现场。目击者之一不顾禁令将该片公诸于众。在片中人们看到躺在解剖台上的是一个身材矮小,面...八十年代中,一些西方国家的电视台曾播放过一部“解剖外星人”的纪录片。据说该片是美国军方在六十年代拍摄的,密级AAA,杜鲁门总统曾亲临解剖现场。目击者之一不顾禁令将该片公诸于众。在片中人们看到躺在解剖台上的是一个身材矮小,面目怪异的人形物。片子播出后着实轰动不小,但当人们尚未平静下来时,真相大白:美国军方从未有过AAA的保密级别(一般说来这是金融债券的等级),而且研究杜鲁门生平的机构也作证杜氏从未有亲眼目睹外星人的荣幸。这只是某些好事者玩弄的又一个科学骗局。自从科技的发展使人们对天外的世界有所了解之后,有关外星人的猜测、臆断和传说便纷纷扬扬,这个骗局可能就是在虚荣心和功利心驱使下的一个极端的例子。夜阑人静之时,遥远的星光,深邃的苍穹引发了人们无穷的想象力。亦幻亦真的UFO,好莱坞的经典E.T.把人们引入一个又一个现代神话故事、但是,放下神话,人们还是要问:“外星人兄弟,你在哪里?” 今年七月份美国《读者文摘》亚洲版刊登的ARE WE AIONE IN THEUNIVERSE一文向人们展示了现实与神话间的距离:寻找地球外智慧生命的最新进展和成果。读者可以详细了解寻找外星人的理论依据、最新技术和主要障碍。更重要的是,本文向我们展示了一种科学精神:脚踏大地,放眼太空。展开更多
We study the global star formation law, the relation between the gas and star formation rate （SFR） in a sample of 130 local galaxies with infrared （IR） luminosities spanning over three orders of magnitude （109-10...We study the global star formation law, the relation between the gas and star formation rate （SFR） in a sample of 130 local galaxies with infrared （IR） luminosities spanning over three orders of magnitude （109-1012 Lo）, which includes 91 normal spiral galaxies and 39 （ultra）luminous IR galaxies [（U）LIRGs]. We derive their total （atomic and molecular） gas and dense molecular gas masses using newly available HI, CO and HCN data from the literature. The SFR of galaxies is determined from total IR （8-1000 μm） and 1.4 GHz radio continuum （RC） luminosities. The galaxy disk sizes are defined by the de-convolved elliptical Gaussian FWHM of the RC maps. We derive the galaxy disk-averaged SFRs and various gas surface densities, and investigate their relationships. We find that the galaxy disk-averaged surface density of dense molecular gas mass has the tightest correlation with that of SFR （scatter -0.26 dex）, and is linear in log-log space （power-law slope of N=1.03±0.02） across the full galaxy sample. The correlation between the total gas and SFR surface densities for the full sample has a somewhat larger scatter （-0.48 dex）, and is best fit by a power-law with slope 1.45±0.02. However, the slope changes from -1 when only normal spirals are considered, to -1.5 when more and more （U）LIRGs are included in the fitting. When different CO-to-H2 conversion factors are used to infer molecular gas masses for normal galaxies and （U）LIRGs, the bi-modal relations claimed recently in CO observations of high-redshift galaxies appear to also exist in local populations of star-forming galaxies.展开更多
The evolution of rotating stars with magnetic fields has been studied with focus given to the following aspects: the effects of magnetic fields on equation of state for stellar matter and the thermodynamic quantities;...The evolution of rotating stars with magnetic fields has been studied with focus given to the following aspects: the effects of magnetic fields on equation of state for stellar matter and the thermodynamic quantities; the effects of magnetic energy and pressure on the internal structure of stars. The differences between the structure and evolution of a 15M⊙rotating star with and without magnetic fields are discussed. Our results show that the magnetic fields have an effect on the structure and evolution of the star mainly during the central helium burning phase; and this influences the physical quantities in the stellar envelope where hydrogen and helium are partially ionized. This may influence stellar pulsation.展开更多
文摘八十年代中,一些西方国家的电视台曾播放过一部“解剖外星人”的纪录片。据说该片是美国军方在六十年代拍摄的,密级AAA,杜鲁门总统曾亲临解剖现场。目击者之一不顾禁令将该片公诸于众。在片中人们看到躺在解剖台上的是一个身材矮小,面目怪异的人形物。片子播出后着实轰动不小,但当人们尚未平静下来时,真相大白:美国军方从未有过AAA的保密级别(一般说来这是金融债券的等级),而且研究杜鲁门生平的机构也作证杜氏从未有亲眼目睹外星人的荣幸。这只是某些好事者玩弄的又一个科学骗局。自从科技的发展使人们对天外的世界有所了解之后,有关外星人的猜测、臆断和传说便纷纷扬扬,这个骗局可能就是在虚荣心和功利心驱使下的一个极端的例子。夜阑人静之时,遥远的星光,深邃的苍穹引发了人们无穷的想象力。亦幻亦真的UFO,好莱坞的经典E.T.把人们引入一个又一个现代神话故事、但是,放下神话,人们还是要问:“外星人兄弟,你在哪里?” 今年七月份美国《读者文摘》亚洲版刊登的ARE WE AIONE IN THEUNIVERSE一文向人们展示了现实与神话间的距离:寻找地球外智慧生命的最新进展和成果。读者可以详细了解寻找外星人的理论依据、最新技术和主要障碍。更重要的是,本文向我们展示了一种科学精神:脚踏大地,放眼太空。
基金supported by the National Natural Science Foundation of China (Grant Nos.10833006 and 10621303)the National Basic Research Program of China (Grant No.2007CB815406)
文摘We study the global star formation law, the relation between the gas and star formation rate （SFR） in a sample of 130 local galaxies with infrared （IR） luminosities spanning over three orders of magnitude （109-1012 Lo）, which includes 91 normal spiral galaxies and 39 （ultra）luminous IR galaxies [（U）LIRGs]. We derive their total （atomic and molecular） gas and dense molecular gas masses using newly available HI, CO and HCN data from the literature. The SFR of galaxies is determined from total IR （8-1000 μm） and 1.4 GHz radio continuum （RC） luminosities. The galaxy disk sizes are defined by the de-convolved elliptical Gaussian FWHM of the RC maps. We derive the galaxy disk-averaged SFRs and various gas surface densities, and investigate their relationships. We find that the galaxy disk-averaged surface density of dense molecular gas mass has the tightest correlation with that of SFR （scatter -0.26 dex）, and is linear in log-log space （power-law slope of N=1.03±0.02） across the full galaxy sample. The correlation between the total gas and SFR surface densities for the full sample has a somewhat larger scatter （-0.48 dex）, and is best fit by a power-law with slope 1.45±0.02. However, the slope changes from -1 when only normal spirals are considered, to -1.5 when more and more （U）LIRGs are included in the fitting. When different CO-to-H2 conversion factors are used to infer molecular gas masses for normal galaxies and （U）LIRGs, the bi-modal relations claimed recently in CO observations of high-redshift galaxies appear to also exist in local populations of star-forming galaxies.
基金supported by the National Natural Science Foundation of China(Grant Nos.10933002 and 10878013)the Natural Science Foundation of Yunnan(Grant No.2010CD112)Program for Innovative Research Team(in Science and Technology)in University of Yunnan Province
文摘The evolution of rotating stars with magnetic fields has been studied with focus given to the following aspects: the effects of magnetic fields on equation of state for stellar matter and the thermodynamic quantities; the effects of magnetic energy and pressure on the internal structure of stars. The differences between the structure and evolution of a 15M⊙rotating star with and without magnetic fields are discussed. Our results show that the magnetic fields have an effect on the structure and evolution of the star mainly during the central helium burning phase; and this influences the physical quantities in the stellar envelope where hydrogen and helium are partially ionized. This may influence stellar pulsation.
