• 제목/요약/키워드: Universe

검색결과 968건 처리시간 0.03초

Environmental Dependence of High-redshift Galaxies in CFHTLS W2 Field

  • 백인수;임명신;김재우
    • 천문학회보
    • /
    • 제43권2호
    • /
    • pp.36.1-36.1
    • /
    • 2018
  • Star formation activity of galaxies, along with color and morphology, show significant environmental dependence in local universe, where galaxies in dense environment tend to be more quiescent and redder. However, many studies show that such environmental dependence does not continue at higher redshifts beyond z~1. The question of how the environmental dependence of galactic properties have developed over time is crucial to understanding cosmic galactic evolution. By combining data from Canada-France-Hawaii Telescope Legacy Survey(CFHTLS), Infrared Medium-Deep Survey(IMS), and other surveys, the photometric redshifts of galaxies in CFHTLS W2 field were estimated by fitting spectral energy distribution. The distribution of galaxies was mapped in redshift bins of 0.05 interval from 0.6 to 1.4. For each redshift bin, the number density was mapped. The galaxies in high density regions were grouped into clusters using friend-of-friend method. The color of galaxies were analyzed to study the correlation with redshift as well as environmental difference between field galaxies and cluster member galaxies.

  • PDF

직관적 H-퍼지 반사관계 (Intuitionistic H-Fuzzy Reflexive Relations)

  • K. Hur;H. W. Kang;J. H. Ryou;H. K. Song
    • 한국지능시스템학회:학술대회논문집
    • /
    • 한국퍼지및지능시스템학회 2003년도 춘계 학술대회 학술발표 논문집
    • /
    • pp.33-36
    • /
    • 2003
  • We introduce the subcategory IRel$\_$R/ (H) of IRel (H) consisting of intuitionistic H-fuzzy reflexive relational spaces on sets and we study structures of IRel$\_$R/ (H) in a viewpoint of the topological universe introduce by L.D.Nel. We show that IRel$\_$R/ (H) is a topological universe over Set. Moreover, we show that exponential objects in IRel$\_$R/ (H) are quite different from those in IRel (H) constructed in [7].

  • PDF

범주 IRe $l_{R}$(H)의 부분범주 (Some Subcategories of The Category IRe$l_{R}$(H))

  • K. Hur;H. W. Kang;J. H. Ryou;H. K. Song
    • 한국지능시스템학회:학술대회논문집
    • /
    • 한국퍼지및지능시스템학회 2003년도 춘계 학술대회 학술발표 논문집
    • /
    • pp.29-32
    • /
    • 2003
  • We introduce the subcategories IRe $l_{PR}$ (H), IRe $l_{PO}$ (H) and IRe $l_{E}$(H) of IRe $l_{R}$(H) and study their structures in a viewpoint of the topological universe introduced by L.D.Nel. In particular, the category IRe $l_{R}$(H)(resp. IRe $l_{P}$(H) and IRe $l_{E}$(H)) is a topological universe eve, Set. Moreover, we show that IRe $l_{E}$(H) has exponential objects.ial objects.

  • PDF

Matter Density Distribution Reconstruction of Local Universe with Deep Learning

  • Hong, Sungwook E.;Kim, Juhan;Jeong, Donghui;Hwang, Ho Seong
    • 천문학회보
    • /
    • 제44권2호
    • /
    • pp.53.4-53.4
    • /
    • 2019
  • We reconstruct the underlying dark matter (DM) density distribution of the local universe within 20Mpc/h cubic box by using the galaxy position and peculiar velocity. About 1,000 subboxes in the Illustris-TNG cosmological simulation are used to train the relation between DM density distribution and galaxy properties by using UNet-like convolutional neural network (CNN). The estimated DM density distributions have a good agreement with their truth values in terms of pixel-to-pixel correlation, the probability distribution of DM density, and matter power spectrum. We apply the trained CNN architecture to the galaxy properties from the Cosmicflows-3 catalogue to reconstruct the DM density distribution of the local universe. The reconstructed DM density distribution can be used to understand the evolution and fate of our local environment.

  • PDF

Model-independent constraints on the light-curve parameters and reconstructions of the expansion history from Type Ia supernovae

  • 구한울
    • 천문학회보
    • /
    • 제44권2호
    • /
    • pp.54.1-54.1
    • /
    • 2019
  • We use iterative smoothing reconstruction method along with exploring in the parameter space of the light curves of the JLA supernova compilation (Joint Light-curve Analysis) to simultaneously reconstruct the expansion history of the universe as well as putting constrains on the light curve parameters without assuming any cosmological model. Our constraints on the light curve parameters of the JLA from our model-independent analysis seems to be closely in agreement with results assuming ΛCDM cosmology or using Chevallier-Polarski-Linder (CPL) parametrization for the equation of state of dark energy. This implies that there is no hidden significant feature in the data that could be neglected by cosmology model assumption. The reconstructed expansion history of the universe and properties of dark energy seems to be in good agreement with expectations of the standard ΛCDM model. Our results also indicate that the data allows a considerable flexibility for expansion history of the universe.

  • PDF

Star formation beyond z=0 and its role in the multiverse

  • Oh, Boon Kiat
    • 천문학회보
    • /
    • 제45권1호
    • /
    • pp.48.1-48.1
    • /
    • 2020
  • The cosmological constant is accountable for the accelerated expansion of our Universe. Observational data have provided a tight constraint on the cosmic star formation history from z = 8 to the present. What happens to the star formation rate beyond z=0? I will discuss the star formation rates, along with the properties of the intergalactic mediumfrom our suite of simulations into the future. Since Lambda becomes dominant in the future of our universe, I further simulate counter-factual universes to assign anthropic weights to each universe within the multiverse setting. I will argue that using the asymptotic star formation efficiency as weights, we almost double previous estimates of observers living in universes similar to ours. The expected value of the energy density of Lambda is also closer to the observed value. I will also discuss potential future works to improve the applicability of the anthropic reasoning of the cosmological constant.

  • PDF

nfrared Weak-lensing Detection of an Emerging Galaxy Cluster SpARCSJ1049+56 at z=1.71

  • Finner, Kyle;Jee, Myungkook
    • 천문학회보
    • /
    • 제45권1호
    • /
    • pp.29.4-29.4
    • /
    • 2020
  • Structure in the universe forms hierarchically with the small scales forming first and merging into larger scales. Galaxy clusters are at the pinnacle of the formation process. Peering far into the universe, we can observe galaxy clusters early in their evolution. SpARCSJ1049+56 is a galaxy cluster located at a redshift of 1.71. It has been shown to be rich in cluster galaxies, to have intense star formation, and to have a significant amount of molecular gas. Through careful control of systematics, we detected the weak-lensing signal from this distant galaxy cluster. I will present our HST infrared weak-lensing detection of the cluster with a focus on the method. Our lensing analysis found that the cluster is massive and is rare in a LambdaCDM universe. I will also present the Chandra X-ray discovery of cold gas coincident with the intense star formation and discuss the implications of the detection.

  • PDF

From dark matter to baryons in a simulated universe via machine learning

  • Jo, Yongseok
    • 천문학회보
    • /
    • 제45권1호
    • /
    • pp.50.2-50.2
    • /
    • 2020
  • The dark matter (DM) only simulations have been exploited to study e.g. the large scale structures and properties of a halo. In a baryon side, the high-resolution hydrodynamic simulation such as IllustrisTNG has helped extend the physics of gas along with stars and DM. However, the expansive computational cost of hydrodynamic simulations limits the size of a simulated universe whereas DM-only simulations can generate the universe of the cosmological horizon size approximately. I will introduce a pipeline to estimate baryonic properties of a galaxy inside a dark matter (DM) halo in DM-only simulations using a machine trained on high-resolution hydrodynamic simulations. An extremely randomized tree (ERT) algorithm is used together with multiple novel improvements such as a refined error function in machine training and two-stage learning. By applying our machine to the DM-only simulation of a large volume, I then validate the pipeline that rapidly generates a galaxy catalog from a DM halo catalog using the correlations the machine found in hydrodynamic simulations. I will discuss the benefits that machine-based approaches like this entail, as well as suggestions to raise the scientific potential of such approaches.

  • PDF

허준(許浚)의 자연관(自然觀) - 『동의보감(東醫寶鑑)』을 중심으로 - (Heojun's Outlook on Nature)

  • 박성규;김수중;김남일
    • 한국의사학회지
    • /
    • 제18권2호
    • /
    • pp.197-227
    • /
    • 2005
  • Heojun was the top scientist on Medicine in the 16th and 17th centuries and wrote the Dongeubogam describing the top-level medical theory and technology. So far, his outlook on nature has been disregarded even though his medicine is still effective. Through this study, I would like to know if his outlook on nature as well as his medicine is still effective. The conclusions are as follows: 1. According to his output, the origin of the universe started from the spinning of One Gi(一氣) which is quite different from Hawking's theory. Hawking assumed that the origin of the universe started from the Big-bang and will end to the Big-crunch. However, the current report on the origin of a star is quite similar to Heojun's theory and we acknowledge that his view on the origin of the universe is still effective. 2. According to his output, the universe repeats expanding and contracting forever while Hawking assumed it will come to the end, the Big-crunch, based on the expanding universe theory. Some scientists assists that Hawking's assumption should have some contradictions. Now, we acknowledge that Heojun's universal cycling theory which corresponds with modern physical theories is still effective, which would lead to a new environmental movement. 3. His view on the structure of the universe is quite different from the output of the current science, which results from his thought that the nature should be reviewed from the point of human's view. His view on the structure will be able to be updated based on the output of the current science. 4. The universe analogy started from the East Asian area as well as the Greek and Roman area in the ancient. The idea has disappeared since the scientific revolution era in the West while the idea has been deepened and abundant in the East and has become one of the major philosophical bases. Heojun emphasized its importance from the beginning of his book. 5. The nation analogy has been popular all times and places. According to his output, governing a country is like controlling one's body. 6. According to Needham's output, the universe analogy and the nation analogy were based on the ancient developed alchemy. And Harper assumed that Taiosm was based on the macrobiotic hygiene which was developed by the ancient developed alchemists. We acknowledge that xian(仙) cult, macrobiotic hygiene, medicine, alchemy and the ancient philosophy started from our ancients. Heojun's output restored our ancient tradition by combining the macrobiotic hygiene and philosophy with medicine. 7. Roughly predicting yearly weather would be unacceptable by the current scientist but Heojun's yearly weather forecast is still used in the clinic and seems effective to prepare from any epidemic disease. 8. 'Day and Night' and Four seasons are the most important factors to the macrobiotic hygiene according to the Dongeubogam. The new environmental movements should be based on the most important factors, otherwise the human beings as well as the environment would fail to survive. 9. Wind, Coldness, Heat, Humidity, Dryness and Fire represents weather. The six weather factors represent one of six phases of a year which is decided by the areal factors. Heojun preferred the six factors generated in the body itself to them from the outside. He thought a human being was a universe and the six factors generated in the body responded to the factors of the outside. 10. According to his output, Heat and Humidity are the most important factors which make a human being ill. 11. Life span, disease, food, and dwelling are dependent upon the geographical feature, according to Heojun's output. In addition, one's appearance and his five viscera and the six entrails depend on the food as well as the geographical feature. 12. Heath is related with the environment and they effects upon each other. If one is weak, he will be deeply effected by the nature. On the other hand, if one is strong, he will effect on the nature. That's why people live together. 13. According to Heojun's work, the society is an important factor comprising the environment. During a peaceful era, the society becomes stable and human beings are stable as well while they will be on fire during a chaotic era. 14. Medicine deals with human beings who live in the nature, so any medical book cannot be excellent unless it has any description on the nature. Heojun's outlook on the nature turned out to be logical and suitable even from the point of the current view and it is still effective as if his clinical knowledge and technology are still effective. Something unsuitable may be substituted with the output of the current science.

  • PDF

『전경』에 나타난 입문의례에 관한 연구 (A Study on the Entrance Rituals seen in the 『Jeon-Gyeong』)

  • 김태수
    • 대순사상논총
    • /
    • 제24_2집
    • /
    • pp.85-115
    • /
    • 2015
  • The Reordering of the Universe(天地公事) pursuing the Latter world(後天)'s ideal world while denying the Former world(先天) is composed of enormous rituals. The Dosu(度數) is formed through these rituals and the world is transformed according to the Dosu. The people who follow the Sangje(上帝), the subject of this universe reordering and also participate in the Reordering of the Universe are called as the followers. The follower group can be said as a ritual group in the aspect that they participate in the ritual for the Reordering of the Universe. They not only observed the rituals but also actively participated in them, so took certain roles in forming the Dosu. That is, they performed certain, given roles in developing the rituals, or actively proposed their ideas under the Sangje's leadership, and participated in the process realizing the Dosu. Therefore it can be said that they were a group initiatively participating in the process overcoming the Former world's Sangguk(相克) world, and making the latter world's ideal world. It seemed that the followers at that time might have gone through a certain entrance ritual process in order to join in such a follower group. The 『Jeon-Gyeong』 recorded the entrance rituals of a man called as Cha Gyeong Seok among tremendous followers relatively in detail. According to the 『Jeon-Gyeong』, he first had to get a unique test in the entrance process, and the test was proceeded in several stages: the wisdom test reflecting the Sangje's unusual intelligence, the patience test to endure physical, psychological pains for the great ethic, and the test to evaluate the testee's ability to give up past oneself and to follow the Sangje with a new body & mind. In the process separating himself from the past his appearance, Gyeong-Seok, the candidate to enter, faced a liminal situation, and then performed the incorporation rite. In this process, the purification rite going him out of the past relationship of benefits & grudges was performed, and he was given the regulations to comply as a member of the follower group. Through such serial processes, his entrance in the follower group was allowed. What requested to the candidate in this entrance process was the severance from one's past. For that, the candidate was needed to go out of his past life habits, to free from the relationship of benefits and grudges, and to sever him from his past faults. Such severance was the precondition for him to go out of the Former world's negative reality and to break from the Sanggeuk habits. Another thing requesting to the candidate as well as the severance from his past was to establish a new ideal. The new ideal should be matched with the ideal of the Reordering of the Universe whose main ideology was the Haewon-Sangsaeng(解冤相生). Such ideal can be said as the driving force to proceed toward the new ideal world of Latter World. And the candidate was requested to purify his mind and to participate in the Universe Fair Judgement (天地公庭). That can be said as an important condition for the new member directly to participate in the ritual of the Reordering of the Universe dramatically transforming the world. Finally, the candidate was given the regulations for his ascetic practice(修道) as well as his participation in the Reordering, and was requested to comply them. After becoming a member of this follower group, one had to practice his asceticism through the compliance with such regulations and the training of mantras(呪文) in order to accomplish the goal called as Dotong(道通). By fulfilling these requirements, the newly entered member could have the qualification to perform a certain role in the ritual of the Reordering of the Universe, and could accomplish his religious ideal.