나이가 많은 항성계의 측분광학적 진화 = (The) spectrophotometric evolution of old stellar systems

국문 초록 (Abstract)

다양한 나이와 금속함량을 가지는 단일 항성 종족에 대한 원자외선에서부터 근적외선에 이르기까지의 분광 지수, 측광 색지수, 표면 밝기 요동 등급 및 색지수 등의 값들을 이론적인 종족 진화 합성방법을 통해 알아보았다. 이 모델은 처음으로 나이와 금속함량에 따른 수평계열성의 색분포의 체계적인 변화를 고려하였다.
우리 모델은 Hβ 지수 뿐만 아니라 자외선과 몇몇 가시광 영역의 색지수들이 온도가 높은 푸른수평계열성들에 의해 크게 영향받는다는 것을 보여준다. 온도가 높은 푸른수평계열성들의 기여로 인해, 주어진 나이에서 금속함량이 커질수록, 자외선 색지수와 몇몇 가시광색지수는 단순히 증가하지 않으며, Hβ 지수 또한 단순히 감소하지 않는다. 우리는 이러한 측·분광학적 지수증의 일부가 수평계열성의 색분포에 상당히 민감한 것을 밝혀내었다.
우리은하와 M87, NGC 4472, NGC 1399와 같은 거대 타원은하내의 구상성단계에 대한 관측 비교를 통해, 우리는 Hβ 지수와 금속함량 관계의 체계적인 변화를 발견하였으며, 이 양상은 가시광 색지수와 금속함량의 관계에서도 마찬가지로 나타났다. 우리 모델은 이러한 체계적인 차이가 거대 타원은하내의 구상성단계가 우리은하 구상성단계보다 평균적으로 20∼40 억년정도 나이가 더 많다면, 잘 설명됨을 제시한다. 외부 은하 구상성단계에 대한 지상 대형망원경과 자외선우주망원경을 이용한 차후 관측들을 통해, 이것이 분명 나이 차이 때문인지 아니면 다른 설명도 가능한지를 살펴보아야 할 것이다.

다국어 초록 (Multilingual Abstract)

The theoretical integrated spectrophotometric quantities, such as spectral indices, broadband colors, and surface brightness fluctuation magnitudes and colors, ranging from far-UV to near-IR are estimated for simple stellar populations at various stages of age and metallicity from the evolutionary population synthesis. These models take into account, for the first time, the detailed systematic variation of horizontal-branch (HB) morphology with age and metallicity.
Our models present that UV and some optical colors as well as the Hβ index are significantly affected by the presence of blue HB stars. Because of the contribution from blue HB stars, UV and some optical colors do not monotonically become redder, and the Hβ does not simply decrease as metallicity increases at a given age. Instead, we find that some of those spectrophotometric quantities are intensely dependent on the HB morphology.
The comparison of the observations of the globular cluster system in the Milky Way Galaxy with those in giant elliptical galaxies, such as M87, NGC 4472, and NGC 1399 reveals some systematic shifts in the Hβ - metallicity planes, and consistent features appear in some optical broadband colors versus metallicity planes. Our models suggest that this systematic difference can be explained if the mean age of globular cluster systems in giant elliptical galaxies is, on an average, several billion years older than the Galactic counterpart. Further observations of globular cluster systems in the external galaxies from the large ground-based telescopes and space UV facilities will enable us to clarify whether this difference is indeed due to the age difference or whether other explanations are also possible.

목차 (Table of Contents)

• Contents
• Acknowledgement = i
• Contents = ix
• List of Figures = xii
• Abstract = xxiv
• 1. INTRODUCTION = 1
• 1.1 Purpose of the dissertation = 1
• 1.1.1 Historical background = 3
• 1.1.2 Previous works = 4
• 1.2 The cornerstone of old stellar systems : Globular clusters = 5
• 1.2.1 Information from the typical CMD of a Galactic globular cluster = 7
• 1.2.2 Second parameter effect = 9
• 1.2.3 Globular cluster systems in external galaxies = 10
• 1.3 Dissertation outline = 12
• 2. EVOLUTIONARY POPULATION SYNTHESIS = 13
• 2.1 Introduction = 13
• 2.2 Ingredients = 14
• 2.2.1 Isochrones = 14
• 2.2.2 Post-RGB evolutionary tracks = 17
• 2.2.3 Flux and Color libraries = 18
• 2.2.4 Z - [Fe/H] conversion = 18
• 3. SPECTROSCOPIC EVOLUTION = 20
• 3.1 Introduction = 20
• 3.2 Calculations of integrated spectroscopic values = 23
• 3.2.1 Population models without post-RGB stars = 24
• 3.2.2 Population models with post-RGB stars = 28
• 3.3 Comparison with observations = 47
• 3.3.1 Test of the models via Galactic globular clusters = 47
• 3.3.2 Comparison with globular cluster system in M31 = 61
• 3.3.3 Comparison with globular cluster system in M87 = 68
• 3.3.4 Comparison with globular cluster system in NGC 4472 = 73
• 3.3.5 Comparison with globular cluster system in NGC 1399 = 76
• 4. PHOTOMETRIC EVOLUTION : BROADBAND COLORS = 83
• 4.1 Introduction = 83
• 4.2 Calculations of integrated photometric magnitudes and colors = 84
• 4.2.1 Population models with and without post-RGB stars = 86
• 4.2.2 Washington filter systems = 97
• 4.2.3 UV systems = 103
• 4.3 Comparison with observations = 122
• 4.3.1 Test of the models via Galactic globular clusters = 122
• 4.3.1.1 Optical to near-IR data = 122
• 4.3.1.2 UV data = 126
• 4.3.2 Comparison with Globular cluster system in M31 = 128
• 4.3.2.1 Optical to near-IR data = 128
• 4.3.2.2 UV data = 133
• 4.3.3 Comparison with globular cluster system in M87 = 143
• 4.3.4 Comparison with globular cluster system in NGC 4472 = 156
• 4.3.5 Comparison with globular cluster system in NGC 1399 = 161
• 5. PHOTOMETRIC EVOLUTION : SURFACE BRIGHTNESS FLUCTUATION MAGNITUDES AND COLORS = 165
• 5.1 Introduction = 165
• 5.2 Calculations of integrated SBF magnitudes and colors = 169
• 5.2.1 Population models with and without post-RGB stars = 169
• 5.3 Test of the models via Galactic globular clusters = 186
• 6. CONCLUSIONS AND IMPLICATIONS = 192
• 6.1 Implications for galaxy formation and evolution = 192
• 6.2 Future study = 195
• APPENDIX = 197
• REFERENCES = 286
• Abstract in Korean = 296