http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : Ciesla, F.J. (검색결과 2 건)
- 무료
- 기관 내 무료
- 유료
-
Burgarella Denis,Boquien Mederic,Buat Veronique,Ciesla Laure,Rhoelly Yannick 한국천문학회 2017 天文學論叢 Vol.32 No.1
Modelling and fitting the spectral energy distribution (SED) of galaxies or regions of galaxies is one of the most useful methods available to the astronomer nowadays. By modelling the SEDs and comparing the models to the observations, we can collect important information on the physical processes at play in the formation and evolution of galaxies. The models allow to follow the evolution of the galaxies from their formation on. The versatility of code is crucial because of the diversity of galaxies. The analysis is only relevant and useful if the models can correctly reproduce this diversity now and across (as best as possible) all redshifts. On the other hand, the code needs to run fast to compare several million or tens of millions of models and to select the best (on a probabilistic basis) one that best resembles the observations. With this important point in mind, it seems logical that we should efficiently make use of the computer power available to the average astronomer. For instance, it seems difficult, today, to model and fit SEDs without a parallelized code. We present the new Python version of CIGALE SED fitting code and its characteristics. CIGALE comes in two main flavours: {\it CIGALE Classic} to fit SEDs and {\it CIGALE Model} to create spectra and SEDs of galaxies at all redshifts. The latest can potentially be used in conjunction with galaxy evolution models of galaxy formation and evolution such as semi-analytic ones.
-
Timescales for the evolution of oxygen isotope compositions in the solar nebula
Lyons, J.R.,Bergin, E.A.,Ciesla, F.J.,Davis, A.M.,Desch, S.J.,Hashizume, K.,Lee, J.E. Pergamon Press ; Elsevier Science Ltd 2009 Geochimica et cosmochimica acta Vol.73 No.17
We review two models for the origin of the calcium-, aluminum-rich inclusion (CAI) oxygen isotope mixing line in the solar nebula: (1) CO self-shielding, and (2) chemical mass-independent fractionation (MIF). We consider the timescales associated with formation of an isotopically anomalous water reservoir derived from CO self-shielding, and also the vertical and radial transport timescales of gas and solids in the nebula. The timescales for chemical MIF are very rapid. CO self-shielding models predict that the Sun has Δ<SUP>17</SUP>O<SUB>SMOW</SUB> ∼ -20%% (Clayton, 2002), and chemical mass-independent fractionation models predict Δ<SUP>17</SUP>O<SUB>SMOW</SUB> ∼0%%. Preliminary Genesis results have been reported by McKeegan et al. (McKeegan K. D., Coath C. D., Heber, V., Jarzebinski G., Kallio A. P., Kunihiro T., Mao P. H. and Burnett D. S. (2008b) The oxygen isotopic composition of captured solar wind: first results from the Genesis. EOS Trans. AGU 89(53), Fall Meet. Suppl., P42A-07 (abstr)) and yield a Δ<SUP>17</SUP>O<SUB>SMOW</SUB> of ∼ -25%%, consistent with a CO self-shielding scenario. Assuming that subsequent Genesis analyses support the preliminary results, it then remains to determine the relative contributions of CO self-shielding from the X-point, the surface of the solar nebula and the parent molecular cloud. The relative formation ages of chondritic components can be related to several timescales in the self-shielding theories. Most importantly the age difference of ∼1-3My between CAIs and chondrules is consistent with radial transport from the outer solar nebula (>10AU) to the meteorite-forming region, which supports both the nebular surface and parent cloud self-shielding scenarios. An elevated radiation field intensity is predicted by the surface shielding model, and yields substantial CO photolysis (∼50%) on timescales of 0.1-1My. An elevated radiation field is also consistent with the parent cloud model. The elevated radiation intensities may indicate solar nebula birth in a medium to large cluster, and may be consistent with the injection of <SUP>60</SUP>Fe from a nearby supernova and with the photoevaporative truncation of the solar nebula at KBO orbital distances (∼47AU). CO self-shielding is operative at the X-point even when H<SUB>2</SUB> absorption is included, but it is not yet clear whether the self-shielding signature can be imparted to silicates. A simple analysis of diffusion times shows that oxygen isotope exchange between <SUP>16</SUP>O-depleted nebular H<SUB>2</SUB>O and chondrules during chondrule formation events is rapid (∼minutes), but is also expected to be rapid for most components of CAIs, with the exception of spinel. This is consistent with the observation that spinel grains are often the most <SUP>16</SUP>O-rich component of CAIs, but is only broadly consistent with the greater degree of exchange in other CAI components. Preliminary disk model calculations of self-shielding by N<SUB>2</SUB> demonstrate that large δ<SUP>15</SUP>N enrichments (∼ +800%%) are possible in HCN formed by reaction of N atoms with organic radicals (e.g., CH<SUB>2</SUB>), which may account for <SUP>15</SUP>N-rich hotspots observed in lithic clasts in some carbonaceous chondrites and which lends support to the CO self-shielding model for oxygen isotopes.
ScienceON
코리아스칼라연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
