1. 우주내의 천체
궤이사와 활동은하

2. The Discovery of Quasars
Though these objects emitted radio signals like those from radio galaxies, they were obviously not normal radio galaxies.
Even the most distant photographable galaxies look fuzzy.
These objects, however, looked like stars
Their spectra, however,
were totally unlike stellar
spectra.
So, the objects were called
quasi-stellar objects.

3. The Discovery of Quasars
For a few years, the spectra of quasars were a mystery.
A few unidentifiable emission lines were superimposed on a continuous spectrum.
In 1963, Maarten Schmidt at Hale Observatories tried redshifting the hydrogen Balmer lines to see if they could be made to agree with the lines in 3C273’s spectrum.
At a redshift of 15.8 percent, three lines clicked into place

4. Other quasar spectra quickly yielded to this approach—revealing even larger redshifts.
The redshift z is the change in wavelength divided by the unshifted wavelength .

5. redshifts of quasars The redshifts of quasars can be quite large.
Quasar spectra contain bright emission lines including the Balmer lines of hydrogen.
However, other spectral lines also appear.
Quasar redshifts can be so large that spectral lines are shifted completely out of the visible spectrum, and lines in the ultraviolet can be shifted into the visible spectrum.
The figure shows the spectra of four quasars with relatively low redshifts in which the Hα Balmer line normally seen in the red part of the spectrum is shifted into the infrared.
Many quasars are now known with much larger redshifts

6. The large redshifts of the quasars at great distances.
The redshift of 3C273 is and the redshift of 3C48 is 0.37.
These are large redshifts, but not as large as the largest then known for galaxies—about 0.5.
Soon, however, quasars were found with redshifts much larger than those of any known galaxy.
quasars must have 10 to 1,000 times the luminosity of a large galaxy.
They must be ultraluminous.
fluctuations in quasar brightnesses over times as short as a few hours.
an object cannot change its brightness appreciably in less time than it takes light to cross its diameter.
The rapid fluctuations of quasars show that they are small objects—no more than a few light-hours in diameter.

7. 퀘이사와 활동 은하 1 퀘이사 3C 273 – 큰 적색이동 (0.15 광속)발견
준항성전파원(quasi-stellar Radio source)
QSO(quasi-stellar Object)
 퀘이사 (90% 비 전파원)
[Z=5 (1215A->7000A : V = 0.94C)]
Z = del lambda/lambda = [(1+v/c)/(1-v/c)]1/2 -1
허블 법칙의 거리  엄천난 광도 (1015 Lo – 1011 Lo)
연속 + 방출선 + 흡수선 (보다 적은 Z)
시간 단위의 광도 변화  작은 영역의 방출

11. 퀘이사 스펙트럼
연속 스펙트럼 :
1.almost uniform ;brightness over a range of 1011 in wavelength (energy of nm = that of 300 – 3000 nm =that of 6 – 60 micron)
 unusually blue (at 22mag, 95% of blue stellar obj = QSO, most point source of X-ray = QSO)
 Synchrotron 복사  energetic electron moving through magnetic fields
2. blue bump (visible and UV) dense gas at 104 K
3. brightest in the IR : BB 복사 from warm dust

13. 퀘이사의 방출선
Emitted by gas heated by absorbing UV and X –ray from the source of continous radiation in the quasar
 like gas in an HII or PN
 broad and narrow emission lines
1. narrow line region : H, He, C, N, and other abundant elements
density = one atom per cubic m
 Mo
2. broad line region : 1000 atom per cubic m
few solar mass
closer to the center of the quasar than narrow line region
 both region : large number of small clouds immersed in much hotter gas

15. 크기 : 수 pc 이하  timescale of variable, few years or less

16. Superluminal motion 고 분해능 간섭계 관측에서 여러 부분의 분리가 few milliarcseconds
3C 345 : Z=0.6 =1900 Mpc
= apparent seperations at speeds greater than the speed of light
 superluminal motion = optical illusion

17. Fig. 24.8

18. Fig. 24.9

19. Fig

23. 궤이사 - in Elliptical Galaxy

25. Seyfert Galaxies
In 1943, Mount Wilson astronomer Carl K. Seyfert published his study of spiral galaxies.
Observing at visual wavelengths, he found that some spiral galaxies have small, highly luminous nuclei with peculiar spectra.
These galaxies are now known as Seyfert galaxies

26. Seyfert Galaxies
The spectra of the Seyfert galaxy nuclei contain broad emission lines of highly ionized atoms.
Emission lines suggest a hot, low-density gas.
Ionized atoms suggest that the gas is very excited.
The width of the spectral lines suggests large Doppler shifts produced by high velocities in the nuclei—gas approaching Earth would produce blueshifted spectral lines and gas going away would produce redshifted lines.
The combined light would produce broad spectral lines.
The velocities at the center of Seyfert galaxies are roughly 10,000 km/s—about 30 times greater than velocities at the center of normal galaxies.
Something violent is happening in the cores of Seyfert galaxies

27. 2 활동은하 -1 세이퍼트(Seyfert)은하 중심 핵이 발달된 나선은하 강하고 넓은 방출선 (수천 km 의 선폭)
NGC 1068 :10 광년 중심핵
전파원, X선원, 강한 적외선
수개월의 밝기 변화  작은 영역
엄청난 에너지 방출

28. Seyfert Galaxies
About 2 percent of spiral galaxies appear to be Seyfert galaxies.
They are classified into two categories
Type 1 Seyfert galaxies are very luminous at X-ray and ultraviolet wavelengths and have the typical broad emission lines with sharp, narrow cores.
Rapidly moving gas must be producing the broad part of the lines.
Some lower-velocity gas must also be present to produce the narrow cores of the lines.
Type 2 Seyfert galaxies have much weaker X-ray emission.
Also, they have emission lines that are narrower than those of type 1 Seyfert galaxies but still broader than spectral lines produced by a normal galaxy.

29. Seyfert Galaxies
Astronomers have also discovered that the brilliant nuclei of Seyfert galaxies fluctuate rapidly, especially at X-ray wavelengths.
A Seyfert nucleus can change its X-ray brightness by a significant amount in only minutes.
You have learned that an astronomical body cannot change its brightness in a time shorter than the time it takes light to cross its diameter.
If the Seyfert nucleus can change in a few minutes, then it cannot be larger in diameter than a few light-minutes.
In spite of their small size, the cores of Seyfert galaxies produce tremendous amounts of energy.
The brightest emit a hundred times more energy than the entire Milky Way.
Something in the centers of these galaxies not much bigger than Earth’s orbit produces a galaxy’s worth of energy.

30. Seyfert Galaxies
This statistical evidence hints that Seyfert galaxies may have been triggered into activity by collisions or interactions with companions.
Some Seyferts are expelling matter in oppositely directed jets—a geometry you have seen on smaller scales when matter flows into neutron stars and black holes and forms an accretion disk
Seyfert galaxies contain supermassive black holes—black holes with masses as high as a billion solar masses.

31. Double-Lobed Radio Sources
Beginning in the 1950s : some sources of radio energy in the sky consisted of pairs of radio-bright regions.
the locations of these double-lobed radio sources,
:galaxies located between the two lobes.
Apparently, the galaxies were producing the radio lobes.
First, the geometry suggests that radio lobes are inflated by jets of excited gas emerging from the central galaxy
Second, there is strong evidence that jets and radio lobes are associated with interacting galaxies
The third thing to notice is how the complex shapes of some jets and radio lobes can be explained by the motions of the active galactic nuclei
Finally, the jets seem to be related to matter falling into a central black hole

32. 2 활동은하- 2-2 활동 타원 은하 강한 중심 에너지원 –전파원전파은하
M87:중심전파 관측=> 강한 전파와 6000광년 뻣은 젯트 (2/3 광속)
전파은하의 ¾ : 이중 전파원 –은하자체보다 수십만 광년 떨어진 전파 열편
 은하 중심핵에서 이온가스가 젯트를 따라 열편에 공급
활동은하의 중심핵, 퀘이사 같은 종류

33. 활동 은하 Seyfert I = 퀘이사와 유사, narrow and very broad emission lines
Seyfert 2 ; only narrow emission lines
전파은하
Blazars : 크기가 작고 강한 밝기 변화를 보이는 것이 궤이사와 유사하나, weak emission line이 보이거나 전혀 안보임
IRAS 은하 : 1. Starburst 은하 (M 82)
2. most luminous IRAS Galaxies : Lo in IR ( *normal spiral galaxies, ~ luminosites of quasar )

34. Seyfert Galaxy –NGC7742

38. Obscuring torus 안쪽의 세이퍼트 은하의 핵

39. Fig
전파은하 Cygnus A 의 전파 지도

40. Fig
전파은하 3C 의 전파 등고선

41. Fig

42. Fig
고속 젯트의 관측

43. 활동은하 - Centaurus A

45. Centurus A -- Dusty Galaxy

52. 타원 전파은하

53. NGC6251은하의 여러 전파 영상

54. 퀘이사의 전파 영상 –윗쪽에 퀘이사가 위치하고, 아래로 향한 전파 열편

55. 3 퀘이사의 에너지 근원-1 퀘이사, 활동은하의 중심핵  거대한 블랙홀 관측적 증거 :
M87 중심 밀도 : 300배의 정상 거대 타원은하, 태양근처의 1000배
=> 2.5*109Mo
중심에 소용돌이 치는 뜨거운(10000도) 가스 블랙홀의 물질 유입
NGC3115, NGC4261 : 거대 블랙홀 중심 핵

56. 3 퀘이사의 에너지 근원-2 에너지 – 블랙홀 근처 물질 나선형으로 접근 가속, 압축 수백만도로 가열 블랙홀로 낙하
수백만도로 가열 블랙홀로 낙하
 막대한 에너지 발생 (10%-30%낙하물질)
거대 블랙홀 :109Mo
수십 AU크기 사건 지평선 수개월 변광
주변 뜨거운가스  강한 방출선
강착원반과 젯트

58. 에딩톤 lunimosity L = 30,000(M/Mo) Lo
 max luminosity for a given central mass, without blowing away surrounding material
M/Mo = 1/30,000(L/Lo)  BH mass bigger than this

59. 활동은하 핵에 블랙홀 주변의 강착 원반-A. 서서히 물질이 유입될 경우, B
활동은하 핵에 블랙홀 주변의 강착 원반-A. 서서히 물질이 유입될 경우, B. 물질이 에딩톤 광도한계 가깝게 유입될 경우 안쪽으로 Torus(도넛)가 형성되고 온도가 만도 이상이 되어 UV + visible 파장 영역에 “blue bump”를 형성

60. 젯트 : 회전 강착 원반에 자력선을 따라 방출되 나가는 이온가스 덩어리

61. Fig
젯트로 방출되는 이온가스는 등근 자력선을 만들어 젯트를 작은 각도에 한정되게 한다고 설명

62. model
Unified model: to sort out different kinds of quasars and active galaxies in order to understand how they are related.
Using infrared radiation to penetrate dust, they have observed the core of the double-lobed radio galaxy Cygnus A and found an object much like a quasar.
They have begun to refer to such objects as ‘buried quasars.’

63. 활동은하핵을 보는 방향에 따라 다르게 보이는 활동은하

64. Fig

70. 퀘이사의 분포

71. Fig
V/V_max 방법에의한 퀘이사의 분포

72. >0.5 의 의미는 퀘이사의 분포가 먼 위치, 오래된 것에 치우침을 뜻함

73. 같은 밝기의 퀘이사A,B는 먼 곳(오래 전)에 더 밀집 (또는 C,D)

74. Supermassive BH The universe began 13.7 billion years ago.
The first clouds of gas began forming stars and falling together to form galaxies.
Astronomers suspect that some of that matter formed supermassive black holes at the centers of the star clouds that became the nuclear bulges of galaxies.
The abundance of matter flooding into these black holes could have triggered outbursts that are seen as quasars.
Galaxies were closer together when the universe was young and had not expanded very much.
As they were closer together, the forming galaxies collided more often.
You have learned how collisions between galaxies could throw matter into supermassive black holes and trigger eruptions.

75. gravitational lenses

76. 우주 공간 사이 물질의 존재 : 퀘이사의 흡수선 + 중력렌즈효과
퀘이사의 흡수선 – 퀘이사와 관측자 사이 물질에 의한 것  방출선 보다 작은 적색편이
 사이 물질은 먼 곳(오래 전)에 더 풍부

77. 4 중력 렌즈 효과-1 퀘이사 0957+561 = 두 퀘이사, 같은 Z  중력 렌즈 효과 (아인슈타인의 예측)
 2중, 다중, 원호, 고리의 상들
중력 렌즈원 : 은하들, 암흑물질
중력 렌즈 효과 암흑 물질의 량 추정
 가시광선으로 보이는 물질 보다 수십배 이상의 많은 물질 포함

80. Fig
아인슈타인 링 (전파 관측)

82. Einstein Cross Gravitaional Lens

83. 중력 렌즈

84. 감마-선 폭발체 (Gamma ray Bursts)
수초 –수 분의 감마선 폭발
전 하늘에 무작위 분포 : 우리은하 원반과는 무관
1999, Jan 23 : 감마선 폭발체의 스펙트럼  Z = 1.6(3000 Mpc)
Collapse of a massive star to produce a highly magnetized BH and the merger of two neutron stars(or a neutron star and a BH)