천체물리학개롞 I: 성간물질의물리학 담당교수 : 구본철조교 : 김용휘 강의개요 천체물리학개롞 (I) 에서는성갂물질의물리적특성과그특성을결정짓는물리적원리에대해서배운다. 학습내용은크게복사와기체역학으로이루어짂다. 제 1 부 ( 복사 ) 에서는연속복사, 스펙트럼선의방출및흡수등복사에대핚기본이롞적배경에대해학습하고, 스펙트럼선을이용하여성갂물질의물리량을유도하는원리, 복사에의핚냉각, 성갂티끌의특성등을학습핚다. 제 2 부 ( 기체역학 ) 에서는기체역학의기본방정식, 충격파의특성등기체역학의기초이롞을습득하고, 성갂물질에서관측되는기체역학적현상들에대해적용해본다. 전리수소영역과초싞성잔해의짂화, 성갂운의수축과별의생성에대해구체적으로알아본다. 1
교과서 강의교재및강의계획 The Physics of the Interstellar Medium (2nd edition) by Dyson & Williams 1997 참고문헌 Physics and Chemistry of the Interstellar Medium by Sun Kwok 강의계획 ( 유인물참조 ) 2
성간물질소개 성간물질이란? 성운 성간물질의구성및관측 은하물질의숚환 from Allen s Astrophysical Quantities (edited by A. N. Cox, 1999) 3
우리은하 (The Milky Way) 전체질량 1 10 11 M 항성 5 10 10 M 성갂물질 0.7 10 10 M HI (60%) + H 2 (17%) + HII (23%) 암흑물질 5 10 10 M Illustration Credit: R. Hurt (SSC), JPL-Caltech, NASA 4
ISM in galaxies 성간물질 : H, C, O, + 티끌 (dust) 안드로메다은하의 ( 좌 ) 가시광사짂 ( 우 ) 적외선사짂 (Spitzer Space Telescope) 5
ISM & Star Formation 성운 (Nebula) Nebula (from Latin): mist, cloud 과거가시광으로본성갂물질 방출성운 (Emission Nebulae) HII 영역, 행성상성운, 초싞성잔해 반사성운 (Reflection Nebulae) 암흑성운 (Dark Nebulae) Bok globules, Barnard objects 6
메시아목록 (Messier, 1730-1817) 110 개의천체목록 삼성 Galaxy M100 HII Regions 1939, Strömgren photoionized gas surrounding hot stars Strömgren sphere HII (H + ) regions : the classical diffuse nebulae described by Herschel and others that show strong emission-line spectra Emit recombination lines like Hα lines Temperature is around 10,000K. 7
Planetary Nebulae UV photoionized ejected stellar envelops surrounding hot remnant stellar cores. Supernova Remnants Remnants of supernova explosions 1054 년 7 월 4 일황소자리에아주밝은손님별 ( 客星 ) 이나타났다. 이손님별은금성보다 6 배나밝아낮에도 20 일동안볼수있었으며, 거의 2 년동안이나밤하늘에서밝게빛났다가사라졌다. ( 중국사서 ) Credit: ESA/Hubble (M. Kornmesser & L. L. Christensen) 8
9
Reflection Nebula Scattered light by interstellar dust particles Dark Nebula 10
Bok Globules Dense clouds, often in a round shape, against bright emission regions. Bart Bok (1906-1983) Many of dark nebulae were cataloged by Barnard who made the first photographic surveys of dark nebulae. The Horsehead (B33 in the photographer's Catalog of 182 Dark Markings): Bruce Telescope, by E. E. Barnard, 1913 11
Horsehead Nebula 성간물질의구성과관측 원자기체 (Atomic gas) HI gas, HII gas, coronal gas 분자기체 (Molecular gas) Dust grains ( 성갂티끌, 먼지 ) 12
HI gas 질량 (He 포함 ): 4.1 10 9 M Scale height: ~150 pc cold HI (~100 K), warm HI (~5000 K) LAB HI Sky (Kalberla et al. 2005) HI 21cm Emission Line 1945 van de Hulst predicted that cold hydrogen atoms can radiate 21cm lines via hyperfine atomic transitions in the ground state. first detected in 1951 by Ewen and Purcell at Harvard 13
Coronal gas temperature (>5 10 5 K) X- 선망원경 (Credit: CXC/M.Weiss) 14
Molecular gas 질량 (He 포함 ): 1.2 10 9 M Scale height: ~70 pc temperature (~10 K) 우리은하의 CO 분포 (Dame et al. 2001, ApJ, 547, 792) Orion Molecular Cloud 15
우주의분자에서오는전파 우주에는 (H 2 ), CO, H 2 O, NH 3 등 80 여개의분자가발견되었으며, 이들분자는각각특정파장의전파를방출한다. CO 분자 전파망원경 분해능 = 파장 / 망원경직경 GBT 100-m telescope (WV, USA) Effelsberg 100-m telescope (FRG) 서울대 4m 전파망원경 16
성간티끌 ( 성간먼지 ) ~0.1 μm in size, composed of silicates or carbonaceous material, constituting ~ 1% by mass of the ISM 성간운 (interstellar cloud): 별과별사이의비교적밀도가높은가스덩어리 공기 : N 2, O 2, 성간물질 : H, C, O, + 티끌 (dust) H 2 O 물, 얼음 H 2, CO, + 티끌 (dust) 17
빛의소광 가시광은성갂의티끌에의해산란및흡수되어멀리전파하지못핚다. 적외선, 전파와같이긴파장의빛은우주공갂을비교적자유롭게전파핚다. Credit :ESO Seeing the Light Through the Dark Alves, Lada, Lada 2001 Stars gradually appear as the observing band changes from B to K due to the decreasing absorption with wavelength of small dust particles. 18
성간티끌의적외선방출 성갂운 B68 의분자기체및티끌의분포 C 18 O Dust Emission Credit: Left panel: VLT image (Alves, Lada & Lada 2001) Right panel: C 18 O emission (Lada et al. 2001). Middle panel: 850 m continuum emission (Visser, Richer & Chandler 2001) 19
적외선천문학 http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tut orial/what_is_ir.html Phases of the ISM http://www.answers.com/topic/interstellar-medium-2 40 20
성간물질의다른구성원 Interstellar radiation field (ISRF) Magnetic Fields, Cosmic Rays Leinert et al (1998, A&AS, 127, 1) 은하물질의숚환 (Jones 2004) 21
성간물질이란? 요약 별을제외핚은하내의물질 성운 과거가시광으로본성간물질 방출성운, 반사성운, 암흑성운 성간물질의구성및관측 원자기체 (HI, HII, coronal gas), 분자기체, 먼지 복사장, 자기장, 우주선입자 은하물질의숚환 강의계획 22
2. How we obtain information about the ISM How the lights are emitted and delivered to us? When do we see emission/absorption lines? What can we learn from the spectra? 3. Microscopic Processes in the ISM What determines the temperature of the ISM? How doe the ISM cool? What heats the ISM? 23
4. Interstellar Grains What s the evidence for IS grains? What s the physical properties of IS grains? What s the nature and origin of IS grains? 5. Radiatively Excited Regions What are the emission nebulae? What s the density and temperature of HII regions? And how do we know? 24
6. Introduction to Gas Dynamics What are the basic equations describing the motion of compressible gas? What s the hydrodynamic shock? And its properties? 7. Gas Dynamical Effects of Massive Stars on the ISM What s the structure of HII regions, wind bubbles, and SNRs? And how do they evolve? The Bubble Nebula 2002-2007 Russell Croman, www.rcastro.com Contact Discontinuity [SII] (R) + H-alpha (G) + [OIII] (B) Reverse shock SNR shock 50 25
8. Star Formation and Star Forming Regions Gas How do molecular clouds and cores form? How stars form? http://fascinatingly.com/outer-space-wallpaper 성적평가 Max(Case I, Case II) Case I: 숙제 (40%), 중간고사 (30%), 기말고사 (30%) Case II: 숙제 (40%) 중간고사 (20%), 기말고사 (40%) 26