![Page 1: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/1.jpg)
1) The environment of star formation
2) Theory: low-mass versus high-mass stars
3) The birthplaces of high-mass stars
4) Evolutionary scheme for high-mass stars
5) Conclusion: formation by accretion?
High-mass stars from cradle to first steps: a possible evolutionary sequence
(High-mass M*>10M⊙ L*>104L⊙ B3-O)
![Page 2: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/2.jpg)
The environment of star formation
• Clouds: 10100 pc; 10 K; 10103 cm-3; Av=110; CO,13CO; nCO/nH2
=10-4
• Clumps: 1 pc; 50 K; 105 cm-3; AV=100; CS, C34S; nCS/nH2
=10-8
• Cores: 0.1 pc; 100 K; 107 cm-3; Av=1000; CH3CN, exotic species; nCH3CN/nH2
=10-10
• YSOs signposts: IRAS, masers, UC HIIs
![Page 3: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/3.jpg)
Low-mass VS High-mass
“Standard” (Shu’s) picture:Accretion onto protostarStatic envelope: nR-2
Infalling region: nR-3/2
Protostar: tKH=GM2/R*L*
Accretion: tacc=(dMacc/dt)/M*
– Low-mass stars: tKH > tacc
– High-mass stars: tKH < tacc
High-mass stars reach ZAMS still accreting
![Page 4: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/4.jpg)
![Page 5: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/5.jpg)
Low-mass VS High-mass
“Standard” (Shu’s) picture:Accretion onto protostarStatic envelope: nR-2
Infalling region: nR-3/2
Protostar: tKH=GM2/R*L*
Accretion: tacc=(dMacc/dt)/M*
– Low-mass stars: tKH > tacc
– High-mass stars: tKH < tacc
High-mass stars reach ZAMS still accreting
![Page 6: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/6.jpg)
Problem:Stellar winds + radiation pressure stop accretion at
M*=8 M⊙ how can M*>8 M⊙ form?
Solutions:i. Accretion with
dM/dt(High-M*)>>dM/dt(Low-M*)=10-5 M⊙/yii. Accretion through disks (+outflows)iii. Merging of many low-mass stars
Observations of the natal environment of high-mass stars are necessary to solve this problem!
![Page 7: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/7.jpg)
The search for high-mass YSOsHigh-mass YSOs deeply embedded observations more
difficult than for low-mass YSOs (e.g. S254/7 SFR)Observational problem: to find suitable tracer and target1) What to look for? High-density, high-temper. tracers
high-excitation lines, rare molecules, (sub)mm continuum
2) Where to search for? Young and massive targets:a) UC HIIs: OB stars are in clusters
b) H2O masers without free-free: luminous but without UC HII region
c) IRAS without H2O and UC HII: protostellar phase?
![Page 8: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/8.jpg)
![Page 9: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/9.jpg)
The search for high-mass YSOsHigh-mass YSOs deeply embedded observations more
difficult than for low-mass YSOs (e.g. S254/7 SFR)Observational problem: to find suitable tracer and target1) What to look for? High-density, high-temper. tracers
high-excitation lines, rare molecules, (sub)mm continuum
2) Where to search for? Young and massive targets:a) UC HIIs: OB stars are in clusters
b) H2O masers without free-free: luminous but without UC HII region
c) IRAS without H2O and UC HII: protostellar phase?
![Page 10: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/10.jpg)
Observations
High-mass YSOs: AV > 10 radioNIR needed
• Low angular resolution = single-dish = 10”2’ Effelsberg, Nobeyama, IRAM, JCMT, CSO, NRAO NH3, CO, 13CO, CS, C34S, CH3C2H, CN, HCO+, …
• High angular resolution = interferometers = 0.3”4” VLA, IRAM, Nobeyama, OVRO, BIMA, VLBI NH3, CH3CN, CH3OH, SiO, HCO+, H2O, continuum
![Page 11: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/11.jpg)
General results
Targets surrounded by dense, medium size clumps: 1 pc, 50 K, 105–106 cm-3, 103–104 M⊙
Dense, small cores found close to/around targets: 0.1 pc, >107 cm-3, 40–200 K, 10–103 M⊙
![Page 12: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/12.jpg)
![Page 13: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/13.jpg)
Clumps
Traced by all molecules observed real entities!
• Mclump>Mvirial large B (1mG) needed for equilibrium
• TK R-0.5 heated by source close to centre
• nH2 R-2.6 marginally stable
• dMacc/dt = Mclump/tAD = 10-3–10-2 M⊙/y large accretion rates
clumps may be marginally stable entities (∼105 y) accretion from clumps feeds embedded YSOs
![Page 14: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/14.jpg)
Clumps
Traced by all molecules observed real entities!
• Mclump>Mvirial large B (1mG) needed for equilibrium
• TK R-0.5 heated by source close to centre
• nH2 R-2.6 marginally stable
• dMacc/dt = Mclump/tAD = 10-3–10-2 M⊙/y large accretion rates
clumps may be marginally stable entities (∼105 y) accretion from clumps feeds embedded YSOs
![Page 15: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/15.jpg)
![Page 16: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/16.jpg)
Clumps
Traced by all molecules observed real entities!
• Mclump>Mvirial large B (1mG) needed for equilibrium
• TK R-0.5 heated by source close to centre
• nH2 R-2.6 marginally stable
• dMacc/dt = Mclump/tAD = 10-3–10-2 M⊙/y large accretion rates
clumps may be marginally stable entities (∼105 y) accretion from clumps feeds embedded YSOs
![Page 17: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/17.jpg)
![Page 18: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/18.jpg)
Clumps
Traced by all molecules observed real entities!
• Mclump>Mvirial large B (1mG) needed for equilibrium
• TK R-0.5 heated by source close to centre
• nH2 R-2.6 marginally stable
• dMacc/dt = Mclump/tAD = 10-3–10-2 M⊙/y large accretion rates
clumps may be marginally stable entities (∼105 y) accretion from clumps feeds embedded YSOs
![Page 19: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/19.jpg)
![Page 20: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/20.jpg)
Clumps
Traced by all molecules observed real entities!
• Mclump>Mvirial large B (1mG) needed for equilibrium
• TK R-0.5 heated by source close to centre
• nH2 R-2.6 marginally stable
• dMacc/dt = Mclump/tAD = 10-3–10-2 M⊙/y large accretion rates
clumps may be marginally stable entities (∼105 y) accretion from clumps feeds embedded YSOs
![Page 21: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/21.jpg)
Clumps
Traced by all molecules observed real entities!
• Mclump>Mvirial large B (1mG) needed for equilibrium
• TK R-0.5 heated by source close to centre
• nH2 R-2.6 marginally stable
• dMacc/dt = Mclump/tAD = 10-3–10-2 M⊙/y large accretion rates
clumps may be marginally stable entities (∼105 y) accretion from clumps feeds embedded YSOs
![Page 22: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/22.jpg)
Hot Cores (HCs)
Hot (100–200 K) cores often found close to UC HIIs:• H2O masers and high energy lines large nH2
and TK
• many rare molecules evaporation from dust grains• TK R-3/4 inner energy source• LIRAS 104 L ⊙ embedded OB star• a few HCs contain UC HIIs! OB stars• rotating circumstellar disks found in some HCs• molecular outflows from several HCs
HCs host young ZAMS high-mass stars
![Page 23: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/23.jpg)
Hot Cores (HCs)
Hot (100–200 K) cores often found close to UC HIIs:• H2O masers and high energy lines large nH2
and TK
• many rare molecules evaporation from dust grains• TK R-3/4 inner energy source• LIRAS 104 L ⊙ embedded OB star• a few HCs contain UC HIIs! OB stars• rotating circumstellar disks found in some HCs• molecular outflows from several HCs
HCs host young ZAMS high-mass stars
![Page 24: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/24.jpg)
![Page 25: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/25.jpg)
![Page 26: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/26.jpg)
![Page 27: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/27.jpg)
Hot Cores (HCs)
Hot (100–200 K) cores often found close to UC HIIs:• H2O masers and high energy lines large nH2
and TK
• many rare molecules evaporation from dust grains• TK R-3/4 inner energy source• LIRAS 104 L ⊙ embedded OB star• a few HCs contain UC HIIs! OB stars• rotating circumstellar disks found in some HCs• molecular outflows from several HCs
HCs host young ZAMS high-mass stars
![Page 28: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/28.jpg)
![Page 29: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/29.jpg)
Hot Cores (HCs)
Hot (100–200 K) cores often found close to UC HIIs:• H2O masers and high energy lines large nH2
and TK
• many rare molecules evaporation from dust grains• TK R-3/4 inner energy source• LIRAS 104 L⊙ embedded OB star• a few HCs contain UC HIIs! OB stars• rotating circumstellar disks found in some HCs• molecular outflows from several HCs
HCs host young ZAMS high-mass stars
![Page 30: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/30.jpg)
![Page 31: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/31.jpg)
![Page 32: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/32.jpg)
Hot Cores (HCs)
Hot (100–200 K) cores often found close to UC HIIs:• H2O masers and high energy lines large nH2
and TK
• many rare molecules evaporation from dust grains• TK R-3/4 inner energy source• LIRAS 104 L⊙ embedded OB star• a few HCs contain UC HIIs! OB stars• rotating circumstellar disks found in some HCs• molecular outflows from several HCs
HCs host young ZAMS high-mass stars
![Page 33: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/33.jpg)
![Page 34: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/34.jpg)
![Page 35: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/35.jpg)
![Page 36: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/36.jpg)
![Page 37: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/37.jpg)
![Page 38: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/38.jpg)
![Page 39: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/39.jpg)
![Page 40: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/40.jpg)
Hot Cores (HCs)
Hot (100–200 K) cores often found close to UC HIIs:• H2O masers and high energy lines large nH2
and TK
• many rare molecules evaporation from dust grains• TK R-3/4 inner energy source• LIRAS 104 L⊙ embedded OB star• a few HCs contain UC HIIs! OB stars• rotating circumstellar disks found in some HCs• molecular outflows from several HCs
HCs host young ZAMS high-mass stars
![Page 41: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/41.jpg)
Beuther et al. (2002)
![Page 42: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/42.jpg)
Hot Cores (HCs)
Hot (100–200 K) cores often found close to UC HIIs:• H2O masers and high energy lines large nH2
and TK
• many rare molecules evaporation from dust grains• TK R-3/4 inner energy source• LIRAS 104 L⊙ embedded OB star• a few HCs contain UC HIIs! OB stars• rotating circumstellar disks found in some HCs• molecular outflows from several HCs
HCs host young ZAMS high-mass stars
![Page 43: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/43.jpg)
Warm cores (WC)
Mostly towards IRAS sources with [25-12]<0.57 :
• warm (50 K) but dense and massive (10–102 M⊙)
• luminous (LIRAS 104 L⊙) high-mass YSOs
• few H2O masers (no OH masers) prior to HC phase
• no cm continuum emission hypercompact HII?• weak evidence for disks and outflows• interesting candidate: the case of G24.78+0.08
WCs may be “class 0” high-mass sources (?)
![Page 44: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/44.jpg)
![Page 45: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/45.jpg)
Warm cores (WC)
Mostly towards IRAS sources with [25-12]<0.57 :
• warm (50 K) but dense and massive (10–102 M⊙)
• luminous (LIRAS 104 L⊙) high-mass YSOs
• few H2O masers (no OH masers) prior to HC phase
• no cm continuum emission hypercompact HII?• weak evidence for disks and outflows• interesting candidate: the case of G24.78+0.08
WCs may be “class 0” high-mass sources (?)
![Page 46: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/46.jpg)
H2O maser
![Page 47: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/47.jpg)
Warm cores (WC)
Mostly towards IRAS sources with [25-12]<0.57 :
• warm (50 K) but dense and massive (10–102 M⊙)
• luminous (LIRAS 104 L⊙) high-mass YSOs
• few H2O masers (no OH masers) prior to HC phase
• no cm continuum emission hypercompact HII?• weak evidence for disks and outflows• interesting candidate: the case of G24.78+0.08
WCs may be “class 0” high-mass sources (?)
![Page 48: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/48.jpg)
![Page 49: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/49.jpg)
IRAS 23385+6053
![Page 50: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/50.jpg)
Warm cores (WC)
Mostly towards IRAS sources with [25-12]<0.57 :
• warm (50 K) but dense and massive (10–102 M⊙)
• luminous (LIRAS 104 L⊙) high-mass YSOs
• few H2O masers (no OH masers) prior to HC phase
• no cm continuum emission hypercompact HII?• weak evidence for disks and outflows• interesting candidate: the case of G24.78+0.08
WCs may be “class 0” high-mass sources (?)
![Page 51: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/51.jpg)
WC
HC
![Page 52: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/52.jpg)
![Page 53: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/53.jpg)
![Page 54: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/54.jpg)
Warm cores (WC)
Mostly towards IRAS sources with [25-12]<0.57 :
• warm (50 K) but dense and massive (10–102 M⊙)
• luminous (LIRAS 104 L⊙) high-mass YSOs
• few H2O masers (no OH masers) prior to HC phase
• no cm continuum emission hypercompact HII?• weak evidence for disks and outflows• interesting candidate: the case of G24.78+0.08
WCs may be “class 0” high-mass sources (?)
![Page 55: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/55.jpg)
Proposed evolutionary sequence
I. WC: dMacc/dt 10-5 M⊙/y squelches UC HII; e.g. IRAS 23385+6053: 104 L⊙, 40 K, 370 M⊙
II. HC: outflow+disk, non-spherical accretion? e.g. IRAS 20126+4104: 104 L⊙, 200 K, 10 M⊙
III. HC+ small UC HII: outflow+disk remnant, UC HII begins expansion; e.g. G10.47+0.03: 5 105 L⊙, 200 K, 103 M⊙
IV. HC+UC HII: outflow remnant, UC HII destroys HC; e.g. G5.89-0.39: 7 105 L⊙, 100 K, 3 103 M⊙
V. (UC)HII: HC is “evaporated”
![Page 56: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/56.jpg)
IRAS 23385+6053
![Page 57: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/57.jpg)
Proposed evolutionary sequence
I. WC: dMacc/dt 10-5 M⊙/y squelches UC HII; e.g. IRAS 23385+6053: 104 L⊙, 40 K, 370 M⊙
II. HC: outflow+disk, non-spherical accretion? e.g. IRAS 20126+4104: 104 L⊙, 200 K, 10 M⊙
III. HC+ small UC HII: outflow+disk remnant, UC HII begins expansion; e.g. G10.47+0.03: 5 105 L⊙, 200 K, 103 M⊙
IV. HC+UC HII: outflow remnant, UC HII destroys HC; e.g. G5.89-0.39: 7 105 L⊙, 100 K, 3 103 M⊙
V. (UC)HII: HC is “evaporated”
![Page 58: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/58.jpg)
![Page 59: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/59.jpg)
Proposed evolutionary sequence
I. WC: dMacc/dt 10-5 M⊙/y squelches UC HII; e.g. IRAS 23385+6053: 104 L⊙, 40 K, 370 M⊙
II. HC: outflow+disk, non-spherical accretion? e.g. IRAS 20126+4104: 104 L⊙, 200 K, 10 M⊙
III. HC+ small UC HII: outflow+disk remnant, UC HII begins expansion; e.g. G10.47+0.03: 5 105 L⊙, 200 K, 103 M⊙
IV. HC+UC HII: outflow remnant, UC HII destroys HC; e.g. G5.89-0.39: 7 105 L⊙, 100 K, 3 103 M⊙
V. (UC)HII: HC is “evaporated”
![Page 60: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/60.jpg)
![Page 61: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/61.jpg)
Proposed evolutionary sequence
I. WC: dMacc/dt 10-5 M⊙/y squelches UC HII; e.g. IRAS 23385+6053: 104 L⊙, 40 K, 370 M⊙
II. HC: outflow+disk, non-spherical accretion? e.g. IRAS 20126+4104: 104 L⊙, 200 K, 10 M⊙
III. HC+ small UC HII: outflow+disk remnant, UC HII begins expansion; e.g. G10.47+0.03: 5 105 L⊙, 200 K, 103 M⊙
IV. HC+UC HII: outflow remnant, UC HII destroys HC; e.g. G5.89-0.39: 7 105 L⊙, 100 K, 3 103 M⊙
V. (UC)HII: HC is “evaporated”
![Page 62: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/62.jpg)
![Page 63: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/63.jpg)
Proposed evolutionary sequence
I. WC: dMacc/dt 10-5 M⊙/y squelches UC HII; e.g. IRAS 23385+6053: 104 L⊙, 40 K, 370 M⊙
II. HC: outflow+disk, non-spherical accretion? e.g. IRAS 20126+4104: 104 L⊙, 200 K, 10 M⊙
III. HC+ small UC HII: outflow+disk remnant, UC HII begins expansion; e.g. G10.47+0.03: 5 105 L⊙, 200 K, 103 M⊙
IV. HC+UC HII: outflow remnant, UC HII destroys HC; e.g. G5.89-0.39: 7 105 L⊙, 100 K, 3 103 M⊙
V. (UC)HII: HC is “evaporated”
![Page 64: The environment of star formation Theory: low-mass versus high-mass stars](https://reader036.vdocument.in/reader036/viewer/2022062322/5681487f550346895db58bb7/html5/thumbnails/64.jpg)
Conclusions
High-mass YSOs are associated with:
• large accretion rates
• outflows and circumstellar disks
High-mass stars could form through accretion as much as low-mass stars