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Home , CI Tauri, Cygnus OB7, GG Tauri, Gliese 673, L1551 IRS 5, NGC 1999

Index of Astronomical Objects

Constellations M33, 746, 747 Aquila, 115, 433, 488 M51 (NGC 5194), 26, 737, 752, 755 Auriga, 11 M82, 753 Chamaeleon, 103 NGC 185, 747, 748 Crux, 119 NGC 1300, 760 , 509, 545, 547 NGC 1569, 750 , 101 NGC 4111, 739 Monoceros, 63, 104 NGC 4472, 736 , 2 Small Magellanic Cloud, 746, 747 Perseus, 495 , 10 HII Regions λ Orionis, 668 Embedded Clusters 30 Doradus (Tarantula ), 97, 417, 745, ρ Ophiuchi, 94, 98, 106, 411, 415 750, 758, 764 30 Doradus, 97 G192.16−3.82, 544 Arches Cluster, 734 G29.96−0.02, 534 Central Cluster, 734 G34.26+0.15, 531 IC 348, 91, 98, 109, 447 G43.18−0.52, 531 Kleinman-Low (KL) Nebula, 10, 138, 226, G5.89−0.39, 530 229, 233, 237, 455, 508, 513, 535 M8 (), 686 NGC 2023, 96 M16 (), 126, 528, 555 NGC 2024, 96 NGC 1999, 428 NGC 2068, 96 NGC 3603, 97, 417 NGC 2071, 96 NGC 6334F, 493, 496, 512, 531 NGC 2244, 63, 67, 109, 385 NGC 7538, 97, 454 NGC 2264, 104, 107, 109, 121, 363, 686 Orion Bar, 7, 523 NGC 3603, 97, 689 (M42, NGC 1976), 7, 37, 38, NGC 7538, 97 496, 552, 555 Quintuplet Cluster, 734 , 63, 556 R136, 417, 745, 750 S106, 547 S106, 96, 121, 257 S199, 560 S255 / S257, 96 S254 / S255 / S257, 96 S88B, 525 W3(OH), 492, 507, 513 Arp 220, 753, 754, 770 W49, 115, 488, 491, 493, 512, 513 Arp 244 (The Antennae), 755 W49N, 488, 507, 509, 514, 515 Large Magellanic Cloud, 97, 417, 736, 744, W75N, 257, 509 747 VLA 1, 509 Leo I, 747 VLA 2, 509 M31 (Andromeda ), 746, 747, 749 VLA 3, 509 836 Index of Astronomical Objects

Molecular Clouds B2/Middle, 139 ρ Ophiuchi Complex, 73, 92, 110, 358, 560, B2/North, 515 567, 637 Serpens Molecular Cloud, 98 ζ Ophiuchi, 60 L572, 98 B5, 12 Taurus-Auriga Complex, 11, 60, 73, 358, 414 B33 (Horsehead), 222 L1434, 12 B35, 668 L1459, 12 B68, 84 L1489, 76, 78, 173, 359 B335, 60, 84, 215, 362, 363, 446, 454 L1495, 12 Molecular Cloud, 348 L1521, 12 Chamaeleon Molecular Cloud, 103, 676 L1544, 366 Complex, 73, 390 L1551, 15, 444, 452, 453 Cygnus Molecular Cloud, 98, 509 TMC-1, 12, 60, 137, 454 L63, 80 TMC-1C, 15 L260, 75 TMC-2, 12 L984, 98 Ursa Major, 257 L988, 98 Molecular Outflows L1251A, 82 BN-KL, 10 Gum Nebula, 430, 540 DR 21, 545 L204, 257 HH 211, 447, 486 L1688, 81, 92, 359 HH 212, 510, 512 L1709, 81 IRAS 03282, 446 L1712, 81 L1448/mm, 93, 512 L1729, 81 L1551/IRS 5, 444, 446, 448, 452, 545 L1755, 81 L1557, 454 Lupus Molecular Cloud, 101, 110 NGC 2071, 450 B228, 101 OMC-1, 455, 545 M17 (), 222, 223 VLA 1623, 448 Maddalena Cloud, 272 Monoceros Molecular Cloud, 63, 104, 687 OB Associations Orion Molecular Cloud, 2, 60, 63, 115, 222, α Persei (Per OB3), 110, 423 348 θ1 Orionis, 7 L1617, 430 Cassiopeia OB2, 97, 454 L1630, 4, 96, 107, 226, 439, 450 Cassiopeia-Taurus, 110, 423, 567 L1641, 4, 114, 432 Cepheus OB1, 109 NGC 2024, 181, 257 Cepheus OB2, 110, 117, 687 OMC-1, 9 Cepheus OB6, 110 Orion 1.5 South, 138 Collinder 121, 110 Orion A, 4, 113, 251, 348, 428, 432, 455 Cygnus OB2, 569 Orion B, 4, 5, 348 Cygnus OB7, 569 Perseus Molecular Cloud, 81, 91, 98, 414, Gemini OB1, 96, 565 446, 495 Lacerta OB1, 110 B1, 60, 81, 176, 257, 446 Lower Centaurus-Crux, 110, 111 NGC 1333, 12, 495 Monoceros OB1, 104, 109 Rosette Molecular Cloud, 63, 66, 67, 72, 109 Monoceros OB2, 109, 117 Sagittarius Molecular Cloud Orion OB1, 109, 110, 114, 567 A/West, 257 Perseus OB2, 107, 109, 110, 567 B2, 135, 733, 754, 758, 760 Sagittarius OB1, 686 Index of Astronomical Objects 837

Scorpius-Centaurus, 102, 110, 567, 676 BD+65◦ 1637, 688, 689, 705, 709 Serpens OB1, 126 BD+65◦ 1638, 688 Trapezium Cluster (Orion Nebula Cluster), 7, Becklin-Neugebauer (BN) object, 9, 138, 416, 420, 552, 577, 583, 616, 620, 687, 149, 455 689, 690, 734 Betelgeuse (α Orionis), 2 Trumpler 10, 110 BP Tauri, 598, 625, 626, 632, 647, 657 Upper Centaurus-Lupus, 110 CI Tauri, 638, 644, 711 Upper Scorpius, 110, 112, 560 Cohen-Schwartz , 429 Vela OB2, 110 DE Tauri, 611 Open Clusters DF Tauri, 387, 611 α Persei, 118, 614, 615, 672 DG Tauri, 640, 641 Blanco 1, 118 DoAr 21, 637 Collinder 359, 118 DR Tauri, 625, 626, 632, 644, 667 Coma Berenices, 118 EX Lupi, 671 , 11, 118, 120, 392, 515, 600, 614, FM Tauri, 638, 711 629, 673 Fomalhaut (α PsA), 720, 722 IC 1396, 117 FU Orionis, 668 IC 2391, 118 GG Tauri, 653 IC 2602, 118 Gl 229A, 607 Melotte 227, 118 Gliese 229B, 607 NGC 752, 120 GM Aurigae, 650, 652, 657, 706 NGC 2244, 117 HD 100546, 717, 722, 724 NGC 2451, 118 HD 163296, 716 NGC 4755 (), 119 HE 0107−5240, 765, 777 NGC 6475, 118 HH 34/IRS, 440 NGC 6530, 686 HR 4796A, 676, 719, 720, 722 NGC 6611, 126, 687 HR 5999, 101 Pleiades, 11, 118, 120, 121, 126, 415, 600, IRAS 03282+3035, 446 609, 614, 620, 673 IRAS 04016+2610, 359 Praesepe, 118 IRAS 16293−2422, 394 Ursa Major, 118 IRAS 20126+4104, 535, 544 Optical and Embedded IRc2, 9, 138, 226, 237, 250, 455, 513, 514, β Pictoris, 720, 722, 725 545  Eridani, 677, 678, 720, 724 L1448/mm, 93, 446, 473, 510, 512 η Chamaeleontis, 676 L1551/IRS 5, 444, 447 η Orionis, 114 LkHα 198, 705, 708, 715 σ Orionis, 222 LkHα 220, 690 θ1 Orionis C, 7, 417, 418, 542, 552, 555 LkHα 234, 688, 689, 709, 715 ξ Persei, 141 MWC 349, 547 ζ Orionis, 113, 222, 417 Pistol Star, 734 ζ Puppis, 540, 542, 556 PPl 15, 609 155913−2233, 387 PV Cephei, 440 162814−2427, 389 Rigel (β Orionis), 2 51 Pegasi, 678 RNO 43, 440 AB Aurigae, 693, 705, 708, 711, 715, 717 (S CrA), 644 (α Tauri), 11 S Monoceros, 104, 121, 385 AS 353A, 433, 640 S106 IRS4, 96 BD+40◦ 4124, 97, 417, 689 S255/IR, 96 838 Subject Index

Sagittarius A∗, 138, 162, 222, 257, 733 Scorpius R5, 106 SR 20, 92 Taurus R1/R2, 106 SR 24, 92 Taurus-Orion R1, 106 SSV 13 (SVS 13), 149, 495, 510 Vela R1, 106 , 14, 385, 392, 611 Vela R2, 106 Trapezium, 2, 7, 14, 37, 552 Reflection Nebulae TW Hydrae, 675 NGC 2023, 226 TY Coronae Australis (TY CrA), 390, 391, NGC 7129, 688, 709 395 S106, 96 UX Orionis, 693 UY Aurigae, 393, 654 Stellar Jets and Herbig-Haro Objects V351 Orionis, 703 HH 1/2, 429, 430, 439, 442, 453, 509 V351 Orionis, 701 HH 7-11, 495 V410 Tauri, 662, 667 HH 32, 433, 438, 640, 642 V773 Tauri, 395, 635, 714 HH 33, 440 V830 Tauri, 625, 626, 632 HH 34, 432, 437, 440, 442, 473, 475 , 668 HH 46/47, 430, 437, 453, 556 V1318 Cygni, 97 HH 88, 440 V1515 Cygni, 668 HH 111, 430, 438, 440, 442, 453 V1686 Cygni, 97 HH 211, 447 Vega (α Lyrae), 676, 721, 722 HH 212, 438, 510 VLA 1, 429, 442 VLA 1, 429 WL 12, 92 Supernova Remnants WSB 18, 395 Cassiopeia A, 564 YY Orionis, 644 , 563 Quasars , 564 3C161, 34 Cygnus Superbubble, 568 IC 443, 565, 569 R Associations Lindblad Ring, 567 Canis Majoris R1, 106, 690 Local Bubble, 567 Cassiopeia R1, 106 Cepheus R1, 106 T Associations Cepheus R2, 106 Chamaeleon I/II/III, 103, 105 Monoceros R1, 106, 107 Lupus, 101, 110, 412, 579 Monoceros R2, 106, 363 NGC 1333, 98 Orion R1/R2, 106, 107, 113 Taurus-Auriga, 14, 97, 98, 100, 105, 110, Perseus R1, 106 411, 579, 617, 672 Scorpius R1, 106 TW Hydrae, 98, 675, 719 Subject Index

α-disk models, 343 Artificial viscosity, 377 δ Scuti variables, 704 Associations, stellar, defined, 88 γ-radiation: production in molecular clouds, 185, Asymptotic giant branch, 24 187 Atomic cooling rates, 198 κ-mechanism, 703 Atomic envelope, of clouds: heating and cooling in, Λ-doubling, see hydroxyl 207, see also Atomic Atomic hydrogen (HI) , defined, 16, 43 21 cm line profiles, 32, 34 Absorption of radiation, 45 as probe of magnetic field, 71 Accretion , defined, 320 associated with molecular clouds, 66 Accretion shock, 321 clouds, 34, 38 Activation barrier, 136 distribution in the , 36 Adsorption of molecules, see dust grains energy levels, 33 Alfvén point, 465 in cold neutral medium, 40 Alfvén velocity, defined, 234 in external galaxies, 34 Alfvén waves, 275 ionization by cosmic rays, 188, 189 damping of, 289, 460 origin of 21 cm emission, 32 influence on stellar winds, 460 photoionization by high- stars, 520 torsional, 306 radio recombination lines from, 525 Alfvénic Mach number, defined, 234 scale height in the Milky Way, 40 Ambartsumian, V., 97 shells and supershells of, 567 Ambipolar diffusion, 262 temperature of, 34 during cloud collapse, 299 Atomic oxygen (OI) flux loss during, 282 emission, from stellar jets, 472 time scale for, 284, 286 emission, from T Tauri stars, 641 Ammonia (NH3), 10, 15 far-infrared emission from, 200, 208, 222, as probe of dense cores, 75, 151 520, 709 creation in molecular outflows, 453 fine-structure levels, 198 discovery of in space, 135 in cloud envelopes, 212 inversion transitions, 153, 172, 173 Autoionization of H2, 137 maser emission from, 497 rotational states, 152 Balmer continuum, 625 use in obtaining cloud density and tempera- Balmer series, 32, 36 ture, 171 Band head, of CO emission, 149 Antenna temperature, defined, 799 Barnard, E. E., 11 , defined, 17 Barred galaxies, origin of, 758 Apparent magnitude, defined„ 43 Beam dilution, defined, 799 Array detectors Beam efficiency, 799 near-infrared, 89 Big Bang, 2, 28 use in imaging binary stars, 386 Binary frequency 840 Subject Index

among pre-main-sequence objects, 385 Bowshocks differential, defined, 382 in giant flows, 439 Binary stars in stellar jets, 429 comparison of ages in, 394 spectroscopic signature of, 433 containing compact objects, 28 Boyle’s law, 246 containing intermediate-mass primaries, 689 Bremsstrahlung, defined, 196 disks in, 402 Brightness temperature, defined, 798 dynamical influence of disks, 402 Broadening function, 611, 810 embedded, 392 Brown dwarfs, see also Dust grains encounters between, 116 in the HR diagram, 605 fission hypothesis for, 397 mass-radius relation, 605 observed classes of, 380 problem of origin, 609 orbital relations, 819 spectroscopic properties, 608 pre-main-sequence spectroscopic, 387 Brown dwarfs, defined, 125 properties in T associations, 391 Bullets, in molecular outflows, 447 properties on the , 382 supernovae in, 116 C-shocks, see also Wardle instability tidal circularization in, 392, 404 heating and cooling in, 236 unresolved, effect on the zero-age main se- C-shocks, defined, 235 quence, 121 CAIs (carbon-aluminum-rich inclusions), 570 Bipolar nebulae, 96 Carbon, see Carbon ionization; Ionized carbon Birthline Carbon ionization: as heating source for molecular in associations, 100, 576 clouds, 192 in the HR diagram, 20 Carbon monoxide (CO), 3, 12 theoretical derivation of, 579 as coolant of molecular clouds, 201, 215 Birthrate of stars as molecular gas tracer, 32 as function of Galactocentric radius, 730, 731 as source of stellar opacity, 91 by spectral type, 30 as tracer of molecular gas, 146 in bound clusters, 88 collisional excitation of, 35, 147 in the Galactic center, 733 emission, from giant molecular clouds, 61 in the solar neighborhood, 124, 730, 732 emission, from photodissociation regions, total, in the Milky Way, 29, 61, 730, 731 709 Blaauw, A., 107 gas-phase formation of, 213 Black holes, 24 high abundance in space, 137 Blackbody radiation, 48 in the Milky Way, 32 Blue compact dwarfs, see Irregular galaxies isotopes, 146 Blueing, in UX Ori stars, 693 line profiles, 164 Bohr magneton, defined, 177 photodissociation of, 151, 213 Bok globules, 83 relation to hydrogen column density, 168 Bolometric correction rotational states, 148 for T Tauri stars, 99 use in imaging disks, 651 Bolometric correction, defined, 23 use in obtaining cloud temperature and den- Bolometric flux from a stellar surface, 50 sity, 165 Bolometric luminosity, defined, 16 vibrational states, 149 Bolometric magnitude, defined, 23 Carbon sulfide (CS) Boltzmann relation, for level populations, 147, 795 as probe of dense cores, 75 Bonnor-Ebert mass, defined, 247 depletion onto grains, 76, 139 Bound-bound and bound-free transitions, 818 Central bulge, see Milky Way Subject Index 841

Central molecular zone, 733 Compton Gamma Ray Observatory, 185 Centrifugal potential, 252 Conductivity, of a molecular cloud, 259 Centrifugal winds, theory of, 461 Convection, 20 Cepheid variables, 704 in , see Protostars Champagne flows, 524 Coronagraphic imaging, 720 Charge-coupled detectors (CCDs), 108 Corotation radius, 659 Charge-exchange reaction, 136 , 118 Chemical abundances Cosmic microwave radiation, 166 in dense cores, 137 as heating agent of molecular clouds, 191 near high-mass stars, 138 Cosmic rays Chemical fractionation, of CO, 165 as heating agent of molecular clouds, 187, Chondrules, 570 207, 215 Chromosphere, solar, 457 attenuation in dense gas, 220 Class 0 sources discovery of, 184 modeling of, 361 energy distribution, 185 Class 0 sources, defined, 93 origin, 184 Class I sources Cosmological constant, 776 nature of, 358 Coulomb pressure, 605 Class I sources, defined, 93 Critical density, cosmological, 776 Class II sources, defined, 93 Critical density, for collisional deexcitation, de- Class III sources, defined, 93 fined, 141 Classical Be stars, 692 Critical points, in stellar winds, 466, 540 Classical T Tauri stars, see also Hα; Infrared ex- Crossing shocks, see Jets cess; Veiling; YY Orionis stars Crossing time, in open clusters, 121 variability, 103 Curve of growth, 674 Classical T Tauri stars, defined, 98 Cyanopolyynes, 135 Cloud complexes, see Giant molecular clouds Clusters, see Embedded clusters; Galaxy clusters; Damped Lyman α galaxies, 768 Open clusters Dark cloud complexes, 73 Clusters, stellar, defined, 88 Dark clouds, 4, 11 CN cycle, 353, 601 dispersal of, 413 CNO bi-cycle, 352, 602, 700 internal magnetic field, 80 Coalescence models, see High-mass stars magnetic stabilization of, 270 Cold neutral medium, see Atomic hydrogen within giant molecular clouds, 71 Color Dark energy, 776 of galaxies, 27 Dark haloes, see also Milky Way of stars, 17 Dark matter Color excess evidence for, 774 near-infrared, 91 role in galaxy formation, 774 relation to hydrogen column density, 53 Dead zone, 467 Color excess, defined, 43 Debris disks, 676 evidence for infall from, 724 observed vs. intrinsic, 43 , defined, 792 Color index, defined, 17 Dense cores, 4, 75 Color-color diagram, near-infrared, 89 erosion by stellar winds, 480 Color-color diagram, optical: of galaxies, 750 internal magnetic field, 80, 270 Color-magnitude diagram, defined, 18 internal temperature of, 216 Comoving distance, defined, 766 intrinsic shape, 77 842 Subject Index

observed rotation, 82, 256 Doppler width, 807 problem of origin, 299 Drag force, between charged particles and neutrals, Density waves, pattern speed, 26 260, 290 Depletion of metals, 37 Drift, relative, of charged particles and neutrals, Detection equation, derivation, 799 283, 299 Deuterium Dust envelope, of protostars cosmological production of, 774 temperature in, 323 fusion, in intermediate-mass stars, 695, 700 Dust envelope, of protostars, defined, 321 fusion, in pre-main-sequence stars, 596 Dust grains, see also Molecular hydrogen fusion, in protostars, 332, 349 absorption of heat from gas, 204 primordial, 28 absorption of ultraviolet radiation, 211 thermostat, 334, 579 as causes of metal depletion, 37, 139 Dichroic extinction, 55, 72 as coolant of molecular clouds, 204, 216 Diffraction limit, defined, 387 coagulation and mantle growth, 107, 108 Diffuse clouds, 53, 60 destruction in C-shocks, 455 heating by cosmic rays, 188 electric charge of, 55, 219, 236 Dilution factor, for interstellar radiation, 192, 194 extinction efficiency factor, 51, 194 Dirac theory, 33 extinction from, 44 Disks heating by interstellar radiation, 195, 215 around intermediate-mass stars, 706, 715 in atmospheres, 608 around main-sequence A stars, 720 mass fraction in the interstellar medium, 54 as drivers of winds, 468 mechanical effects of radiation on, 722 centrifugal radius, 308 opacity of, 47, 54, 204 circumbinary, 403, 653 origin, 29 flaring in, 655 polarization from, 54 frequency of occurrence, 654 reddening from, 17, 43 gas efflux from, 550 regeneration in debris disks, 676 in binary stars, see Binary stars sputtering in shocks, 232 irradiation of, 655 thermal emission from, 47, 49, 80, 81, 93 magnetic disruption of, 658 thermal processing of, 717 millimeter imaging of, 651 total cross section, 53 photevaporation of, 547 within HII regions, 528 relation to FU Orionis outbursts, 668 Dust lanes, 11 thermal emission from, 647, 650 correspondence with CO emission, 101 Disks, protostellar Dust photosphere, of protostars, 321 birth of, 336 conditions at, 324 early evolution, 340 Dust temperature, 49, 52, 194, 204, see also J- internal torquing, 342 shocks; Photodissociation regions; Re- spiral arms in, 345 flection nebulae; Water Dispersion relation in atomic envelope of clouds, 207 for magnetosonic waves, 275, 276 in molecular interior of clouds, 215 for self-gravitating gas, 249 Dwarf spheroidal galaxies, 746 for sound waves, 275 Dwarf stars, see Main-sequence stars Dispersion, of pulsar radiation, 731 Dynamical relaxation, in open clusters, 121 Dissociative recombination, 137 Distance modulus, defined, 17 Echelle spectrometers, 433 Doppler effect, 33 Ecliptic, 792 Doppler imaging, 663 Eddington approximation, 586, 817 Subject Index 843

Effective temperature, defined, 16, 18 Forbidden-line emission: from T Tauri stars, 641 Einstein A and B coefficients, derivation of, 795 Forbidden-line transitions, 200 Electron degeneracy pressure Formaldehyde (H2CO): maser emission from, 497 in brown dwarfs, 603 Fragmentation, dynamical, 298, 369, 374, 377, 399 in white dwarfs, 24 Fragmentation, quasi-static, 398, 406 Electron scattering, 819 Free radicals, 158 Elephant trunks, 528 Free-fall time Elliptical galaxies, 26 in pressure-free collapse, 373 dwarf, 746 Free-fall time, defined, 70 morphology of, 737 Free-fall velocity, defined, 296 problem of origin, 770, 776 Free-free emission, see also Bremsstrahlung star formation history of, 744 from HII regions, 528 Embedded clusters from stellar jets, 442 formation time, 96 Free-free transitions, 819 morphology, 96 FU Orionis outbursts, 668 photometric identification, 89 within starburst galaxies, 97 G-dwarf problem, 762 Embedded clusters, defined, 88 Galactic center, 34 Emission measure, 528, 733 bar in, 758 Emissivity, defined, 47 black hole in, 733 Epicyclic frequency, 344, 741 star formation in, 733 Equation of transfer, 47 Galactic clusters, see Open clusters Equatorial coordinates, 792 Galactic coordinates, 794 Equipartition of energy, 72 General luminosity function, 122 Equivalent width, 627 Giant molecular clouds, 2 Escape probability, 174, 211 clumpy substructure, 63 Eulerian description, of fluid motion, 371 distribution in Milky Way, 61 Excitation temperature, defined, 147 formation and destruction, 67, 68 EXors, 671 internal magnetic field, 72 Extinct radionuclides, 570 observed rotation, 250 Extinction, 43 Globular clusters estimated using background stars, 169 in Milky Way, 25 near-infrared, 91 Globular clusters, defined, 117 relation to CO column density, 169 Globules, cometary, 556 relation to hydrogen column density, 63 photoevaporation of, 557 Extinction curve, see Interstellar extinction curve star formation in, 560 Extinction efficiency factor, see Dust grains Gould’s Belt, 567 Graphite, 52 Fermi momentum, 604 Gravitational collapse, see also Inside-out collapse Fermi, E., 186 density and velocity in rotating, 312 Filling factor fluid trajectories in rotating, 309 of gas in the Milky Way, 36 magnetic flux loss during, 299 of gas within a giant molecular cloud, 63 of clouds, induced by supernovae, 569 Fine splitting: in atomic hydrogen, 33 of pressure-free sphere, 371 Fine-structure levels, of atoms, 198 Gravitational radius, 548 Fluorescence, of H2, 145, 225 Gravitational stability Flux density, see Specific flux of cylindrical clouds, 400 Flux freezing, 256, 261 of magnetized clouds, 268 844 Subject Index

of magnetized slabs, 269, 300 production of ultraviolet radiation, 192 of protostellar disks, 343 radiative heating of clouds, 221 of rotating clouds, 255 upper mass limit of, 416 of spherical clouds, 245 High-velocity clouds, 765 of spiral galaxies, 742 HII regions Gunn-Peterson effect, 778 cometary, 512, 531 extragalactic, see Irregular galaxies Hα emission first and second expansions, 520 as measure of star formation activity, 738 in irregular galaxies, 744 from classical T Tauri stars, 98, 626, 636 magnetic field in, 257 from HII regions, 527 radio emission from, 37, 731 from intermediate-mass stars, 687, 691 relation to embedded clusters, 96 from stellar jets, 428 temperature of, 527 from warm ionized medium, 42 ultracompact, see Ultracompact HII regions Hα line, defined, 32 Homologous collapse, 374 H− ion, as source of stellar opacity, 90 Homologous contraction, 593 cosmological production of, 771 Horizontal branch, 24 Habing flux, 193, 221 Hot cores, 416, 512 Haro, G., 428 chemical composition of, 535 Hayashi temperature, 587 masers in, 534 Hayashi track, 589 molecular emission from, 535 Helioseismology, 621 Hot intercloud medium, 42 Henyey track, 595 Hubble constant, defined, 765 Herbig Ae/Be stars, 14, see also Disks; Winds; In- Hubble sequence, 736 frared excess; UX Ori stars; X-rays Hydrogen recombination lines, 9 as drivers of molecular outflows, 97 Hydrostatic equilibrium birth environments of, 686 along magnetic field lines, 264 companions of, 689 in clouds, 242, 251, 400 dust envelopes surrounding, 707 in stars, 19 HI gas around, 710 of HI gas, 40 objective prism searches for, 106 Hydroxyl (OH) optical spectra of, 690 Λ-doubling, 160, 177 pulsations in, 701 as probe of magnetic field, 71, 158, 176 rotation of, 690 creation and destruction of, 189, 232 Herbig, G., 428 discovery of in space, 135 Herbig-Haro objects, 428, see also Jets magnetic hyperfine splitting, 161 associated with high-mass stars, 543 maser emission from, 162, 489, 506, 565, 754 of, 437 rotational states, 158 Hertzsprung-Russell (HR) diagram, defined, 18 HI clouds, see Atomic hydrogen Ideal MHD equation, 261 HI gas, see Atomic hydrogen Infall, see Protostars High-mass stars, see also Herbig-Haro objects; Infrared Astronomical Satellite (IRAS), 4, 13, 76, Molecular outflows; Winds; X-rays 89 as energizers of local hot gas, 191 Infrared companions, 392 clustering of, 416 Infrared excess in the field, 121 decline with age, 672 outflow generation by, 455 in T Tauri stars, 632, 635 problem of origin, 84, 115, 416, 424 lack of, in weak-lined T Tauri stars, 100 Subject Index 845

of Herbig Ae/Be stars, 705 emission, from T Tauri stars, 641 Infrared excess, defined, 91 Irregular galaxies, 26, 736 Infrared filter sequence, 792 Irregular galaxies, Infrared spectral index, defined, 93 amorphous and blue compact, 746 Infrared stars, 13 in large-scale surveys, 766 Initial luminosity function of, 745 attainment in stellar groups, 407 star formation in, 744 calculation of, 123 Isochrones Initial luminosity function, defined, 106 post-main-sequence, 112 Initial mass function (IMF) pre-main-sequence, 21 effect of metallicity on, 763 in stellar groups, 124 J-shocks, defined, 226 in the brown dwarf regime, 126 dissociation and ionization by, 229, 236 Salpeter function, 124 dust temperature in, 232 Initial mass function (IMF), defined, 124 jump conditions for, 812 Inside-out collapse temperature falloff behind, 228 of magnetized clouds, 300 Jeans length of spherical clouds, 293 as upper limit for cloud equilibria, 370 pressure effects in, 298 Jeans length, defined, 249 Instability strip, of intermediate-mass stars, 703 Jeans mass Intensity, see Specific intensity role in cloud collapse, 377 Interferometers, 4 Jeans mass, defined, 249 Interstellar dust, see also Dust grains Jeans swindle, 370 discovery of, 117 Jets, stellar, see also Bowshocks Local Bubble, 42, 192, 567 crossing shocks in, 476 phases, 39 entrainment by, 477 replenishment of, 28 giant flows, 439 Interstellar extinction curve, 44, 89 internal motion of, 437 Interstellar masers, see masers, interstellar mass transport by, 472 Inverse profiles, 644 morphology of, 430 Ion-molecule reactions, 136 radio observations of, 442 Ionization fraction, in clouds relation to Herbig-Haro objects, 428 empirical determination of, 217 working surface in, 473, 476 theory of, 219 Johnson-Morgan filter sequence, 17, 792 Ionization fronts, 7, 230, 521 Joy, A. H., 97, 661 in globules, 555 Ionized calcium (Ca II): emission, from classical T Tauri stars, 98, 628 -Helmholtz instability, 477 Ionized carbon (C II) Kelvin-Helmholtz time, defined, 21 as gas coolant, 34 Kinetic temperature, defined, 148 far-infrared emission from, 39, 200, 208, 222, Kirkhoff’s law, 49, 806 520, 709 Kramers-law opacity, 819 Ionized hydrogen (HII), see HII regions Ionized oxygen (O II): emission, from HII regions, Lagrangian description, of fluid motion, 371 527 Landé g-factor, 177, 179, 665 Ionized oxygen (O VI), 42 Lane-Emden equation, 243, 590 Ionized sulfur (S II) Larson’s law, 74 emission, from stellar jets, 430, 472 Level populations, in two-level system, 794 846 Subject Index

Limb darkening, 810 Mach number, 814 Lindblad’s Ring, 567 Mach reflection, 477 Line broadening, 802 Maclaurin spheroids, 254, 398 of 21-cm line, 34 Magnetic braking of OH lines, 179 of pre-main-sequence stars, 620 within dense cores, 74 Magnetic braking: of molecular clouds, 305, 306 Line narrowing, see Masers Magnetic field, see also Giant molecular clouds; Line wings, for ultraviolet absorption in H2, 212 Dark clouds; Shocks Lithium coupling to gas, 220 absorption, in weak-lined T Tauri stars, 625 decoupling from gas during collapse, 302 as diagnostic of brown dwarfs, 608 mapping through polarization, 56, 81 as indicator of stellar youth, 103 of clouds, observed density dependence, 257 fusion, in pre-main-sequence stars, 598 of main-sequence stars, 619 primordial, 28 of T Tauri stars, 664 Lithium dip, 600 Magnetic flux problem, 262 Lithium edge, 607 Magnetic pinch, 470 Local Bubble, see Interstellar medium Magnetic precursor, 235 Local Group, 746 Magnetic pressure, 69 Local Thermodynamic Equilibrium (LTE), 148, Magnetic reconnection, 262 795 during cloud collapse, 302 relation to optical thickness, 175 Magnetic tension, 69 Lorentz profile, 805 Magnetorotational instability, 660 Luminosity density, comoving, 767 Magnetosonic waves, 275 Luminosity functions, bolometric Magnetostatic equilibrium, of clouds, 263 of stellar clusters, 94 Main-sequence fitting, see Zero-age main sequence of T associations, 105, 411 Main-sequence stars Luminosity functions, bolometric: evolution of, in near-infrared color-color diagrams, 89 407 lifetime, 23, 27 Luminosity jump, 697 Main-sequence stars, defined, 18 Luminous infrared galaxies, 753 Main-sequence turnoff, 67, 111 Lunar occultation, 387 Main-sequence turnon, 105, 112 Lyα Marginal stability, of clouds, 293, 377 absorption, used to determine HI column den- Maser pump, defined, 498 sity, 169 Masers, interstellar, 10 emission, as gas coolant, 39 brightness temperature of, 491 emission, from J-shocks, 231 collisional pumping in, 506 line, defined, 32 gain and saturation, 501 Lyβ: line, defined, 32 geometric beaming in, 505 Lyman α forest, 768 line narrowing in, 504 Lyman band of H2, 145, 169, 214, 225 motion of, 489 Lyman continuum radiation, 36 polarization of, 492 Lyman limit, 519 production behind shocks, 496 Lyman series, 32 radiative pumping in, 506 Lyman-break galaxies, 768 relation to HII regions, 493, 512 Lynds Catalogue, 4 relation to molecular outflows, 512 relation to stellar jets, 509 Mach angle, defined, 476 use in expanding cluster parallax, 514 Mach disk, 433, 477 variability, 493 Subject Index 847

Mass accretion rate, 294, 329 Molecular hydrogen (H2), 2 Mass continuity equation, 69 discovery of in space, 141 Mass function, for binary stars, 388, 821 dissociation of, 144, 187, 195, 209, 213, 709 Massive stars, see High-mass stars distribution in the Milky Way, 36, 732 Mathis, Rumpl, and Nordsiek distribution, 53 excitation in stellar jets, 453 Maxwell-Boltzmann relation, 75, 806 formation on grain surfaces, 136, 145, 209, Mean free path of photons, 47 212 Mean intensity, defined, 45 gas-phase formation of, 146, 231, 771, 776 Mean molecular weight, defined, 38 heating in shocks, 226 Mechanical luminosity, defined, 451 in first core, 318 Megamasers, OH, 754 ionization by cosmic rays, 187, 189, 219 Mergers, galactic, 754 quantum states, 141 Messier Catalogue, 7 Molecular interior, of clouds: heating and cooling Metallicity: in the solar neighborhood, 37 in, 215 Metastable states, of atoms, 231, 429, 527 Molecular lines, as source of stellar opacity, 91 Meteorites, 37, 570 Molecular outflows, 10, 15 Methane (CH4): in brown dwarf atmospheres, 608 bipolar lobes in, 444 Methanol (CH3OH): maser emission from, 496 chemical enrichment in, 138 MHD equation, 258, see also Ideal MHD equation energy and momentum of, 451 MHD waves, see also Alfvén waves; Magnetosonic from Class 0 sources, 93, 446 waves from high-mass stars, 544 as causes of field distortion, 72 relation to stellar jets, 477 effective pressure of, 277, 459 velocity nesting in, 448 mode conversion of, 279 Molecular oxygen (O2): photodissociation of, 215 perturbational analysis of, 272 Molecular ring: in the Milky Way, 36 MHD winds, see Centrifugal winds Momentum flux tensor, see Pressure tensor Microjets, 640, 642 Moving-cluster method, 118 Milky Way, see also Birthrate of stars; Galactic Multiplicity, of stars, see Binary frequency center; Scale height age of disk, 123 Naked T Tauri stars, 100 central bulge, 25, 35 Nested grid, computational techniques, 376 dark halo, 25 Neutral-neutral reactions, 136 differential rotation of HI gas, 34 Neutron stars, 24 disk, 25 (NGC), 4 distributionofHIgas,35 Nonequilibrium cooling, in J-shocks, 230 distribution of HII regions, 37 Nonhomologous collapse, 374 distribution of molecular gas, 34 Nonhomologous contraction, 696 molecular gas content, 28, 61 Nonthermal motion, see Velocity dispersion origin, 28 Normal mode, in an oscillating cloud, 247 spiral structure, 36, 62, 108 Nova outbursts, 29 stellar halo, 25 Nuclear reactions thick disk, 730 cosmological, 28 Minimum-mass solar nebula, 678 in main-sequence stars, 19 Mixing layer, 477 Mixing-length theory, 333 O-type neutral point, 303 Molecular bands, 17 OB associations Molecular clouds, see Dense cores; Giant molecu- ages, 107 lar clouds; Dark clouds distribution in the Milky Way, 108 848 Subject Index

early evolution, 418 formation of, 678 in the HR diagram, 108 Poincaré-Wavre theorem, 251 origin, 97, 111 Poisson’s equation, 41 pattern of formation, 113 Polarization, see also Dust grains problem of origin, 421 in UX Ori stars, 693 relation to giant molecular clouds, 61, 109 measurement of, 54 Ohm’s law, generalized, 258 of cosmic microwave radiation, 780 Olivine, 52 of OH lines, 177, 180 Opacity gap, 321 Polytropes, 243, 590, 591, 596, 821 Open clusters, see also Moving-cluster method Population I, 25 destruction by giant molecular clouds, 121 Population II, 25 distribution in the solar neighborhood, 117 Population III stars, 765 evaporation from, 121 formation of, 776 in the HR diagram, 119 Population inversion, 498, 500 mass segregation in, 121 Population synthesis modeling, 743 problem of origin, 96, 415 Position-velocity diagram Open clusters, defined, 117 of giant molecular clouds, 64 Optical depth, defined, 47 of molecular outflows, 448 Optical thickness: relation to extinction, 47, see Post-main-sequence stars also Radiative trapping evolutionary tracks, 24 Ortho and para states, of H2, 226 winds from, 29 Ortho and para states, of H2O, 156 Post-T Tauri problem, 413, 673 Oscillator strength, 210, 211 Post-T Tauri stars Overstability, 702 in haloes of T associations, 101 Oxygen, see Atomic oxygen; Ionized oxygen; lithium depletion in, 674 Molecular oxygen Post-T Tauri stars, defined, 100 Poynting-Robertson drag, 723 P Cygni profiles, 639 PP chains, 602 PAHs (polycyclic aromatic hydrocarbons), 56 Pre-main-sequence stars, 14, see also Deuterium; Partition function, of CO rotational states, 168, 799 Lithium Pattern speed, see Density waves entropy decrease in, 591 Pedestal feature, in CO emission lines, 444 evolutionary tracks, 20 Penetration probability, for ultraviolet photons, 211 fully convective phase, 586 Phase mixing, 279 growth of radiative core, 593 Photodissociation regions observed rotation of, 614 chemical transformations in, 225 quasi-static contraction of, 20, 584, 697 dust temperature in, 222 winds from, 15 excited by Herbig Ae/Be stars, 709 Pressure equilibrium of interstellar gas, 39, 42 fine-structure emission from, 223 Pressure tensor, 278 Photodissociation regions, defined, 221 Proper distance, defined, 766 Photoelectric heating, 38, 53, 193, 195, 208, 222 Proper motion, defined, 89 Photosphere, defined, 16 Proplyds, 552 Planck function, for specific intensity, 49, 164 Protobinaries, see Binary stars Planetesimals , 680 as sources of dust, 678 Protostars Planetesimals, defined, 680 disappearance of convection in, 348 early evolution, 317 extrasolar, 678 evidence for inward motion, 365 Subject Index 849

evolutionary time scale, 296 , defined, 765 formation of primordial, 777 Reflection nebulae, 4 hydrogen fusion in, 353, 583 dust temperature in, 56 main accretion phase, 319 excited by intermediate-mass stars, 106 mass-radius relation, 329 in T associations, 102 observational search for, 357 polarization in, 54 onset of convection in, 331 relation to stellar jets, 431 population in stellar groups, 407 Reionization , 778 radiation pressure in, 354 Relaxation region, 228 rotation of, 617 Relaxation time, see also Dynamical relaxation Protostars, defined, 22 Resonance lines, defined, 537 Resonant scattering, 231 Q method, 108 , defined, 792 Quasars Rocket effect, 558 as accreting black holes, 780 Rosseland-mean opacity, 816 as background continuum sources, 32, 768, Rotation, stellar, see also Pre-main-sequence stars; 778 Protostars Quasi-static contraction, see Pre-main-sequence as source of line broadening, 808 stars measurement of, 610 of magnetized clouds, 284, 288 on the main sequence, 612 of stars, see Pre-main-sequence stars Rotational backbone of H2O, 157 R associations, defined, 106 of NH3, 153 , defined, 62 Rotational stability, 253, 660 Radiation field, interstellar Rovibrational transitions as heating agent of dust, see Dust grains in CO, 151 components of, 191 in H2, 143 Radiative association, 136 Runaway OB stars, 115 Radiative diffusion equation, 815 Radiative precursor, 228 Radiative recombination, 137 Salpeter,E.E.,124 Radiative trapping Saturation, of CO lines, 164, 166, 168 in a collapsing cloud, 298, 321 Scale height of CO rotational lines, 148, 166, 201 of a disk, defined, 25 of NH3 inversion lines, 173 of HI gas in the Milky Way, 36 Radio emission: from T Tauri stars, 637 of low-mass stars in the Milky Way, 41 Ram pressure, at accretion shock, 328 of open clusters in the solar neighborhood, Rankine-Hugoniot jump conditions, see J-shocks 117 Rarefaction wave, 296, 301, 304, 524 Scattering of radiation, 46 Rayleigh-Jeans approximation, defined, 174 Schmidt law, 735, 739, 751 Recombination coefficient, for hydrogen, 519 Schmidt, M., 735 Recombination epoch, 771 Schrödinger’s equation, 32, 803 Reconnection, see Magnetic reconnection Schwarzschild’s criterion, 332 branch, see Red giant stars Seeing, defined, 387 Red giant stars Selective extinction, defined, 44 in near-infrared color-color diagrams, 89 Self-consistent field method, 253 in the HR diagram, 18, 24 Self-reversed emission lines, 363 Reddening vector, 91 Self-shielding 850 Subject Index

of CO, 146 in HI, 33 of H2, 146 in OH, 159, 176 Shock velocity, defined, 227 in OI, 198 Shocks, interstellar, see also C-shocks; J-shocks Spiral arms, see also Disks; Milky Way; Spiral as sources of molecules, 135, 231, 233 galaxies collisionless, 563 Spiral density waves, see Density waves cushioning by magnetic field, 233 Spiral galaxies nonradiative, 232, 544 gas content, 26 surrounding HII regions, 523 optical spectra of, 736 Silicates, 52 Split monopole, 300 Silicon oxide (SiO), 10 Sputtering, see Dust grains and the 10 µm feature, 52, 708 Starbursts, 97, 416 creation in molecular outflows, 453 circumnuclear, in galaxies, 752 maser emission from, 497 in dwarf irregular galaxies, 749 Singular isothermal sphere, 244 in merging galaxies, 755 Sink cell, 294 relation to galactic bars, 758 Skumanich law, 613, 629 Starless cores, see Dense cores Smoothed-particle hydrodynamics (SPH), 376 Starspots, 611, see also T Tauri stars Solar composition, 37 Steepening, of sound waves, 277 Solar nebula, 570 Stellar structure equations, 326 Solar neighborhood Stokes parameters, 180 gravitational potential, 40 Strömgren filter sequence, 17, 792 density, 41 Strömgren sphere, 519 Solar neighborhood, defined, 25 Super-adiabatic region, 333, 589 Solar wind Supernova remnants effect on cosmic rays, 185 evolution of, 563 MHD waves in, 271 intersection of, 42 variability of, 457 radio emission from, 564, 731, 751 Sonic point, 458 Supernovae, 25, 29 Sound speed, 40 anisotropic, 116 adiabatic, 229, 584 as energizers of HI gas, 42 isothermal, 243 as sources of cosmic rays, 186 Source function, defined, 799 as sources of interstellar gas, 29 Spallation, defined, 184 cloud compression and heating by, 565 Specific flux Surface , defined, 586 from a stellar surface, 50 Specific flux, defined, 16, 45 T associations Specific intensity demise of, 413 from a stellar surface, 49 halo population, 104 Specific intensity, defined, 44 in the HR diagram, 99 Speckle interferometry, 386 properties of older, 675 Spectral energy distribution, stellar T associations, defined, 97 dereddening of, 91 T Tauri stars, see also Disks; Forbidden-line emis- modeling of, 359 sion; Radio emission; Ultraviolet emis- Spectral type, 17 sion; X-rays Spectroscopic parallax, 108 classical, see Classical T Tauri stars Spheroid, see Milky Way cool spots in, 661 Spin- interaction hot spots in, 665 Subject Index 851

irregular variation in, 668 Visual extinction, see Extinction optical spectra of, 625 Voigt profile, 807 weak-lined, see Weak-lined T Tauri stars Tachocline, 621 Walker, M., 105 Theoretical HR diagram, see Hertzsprung-Russell Wardle instability, 237 diagram Warm ionized medium, 42 Thermal emission, see Dust grains Warm neutral medium, 34, 39, 42, 519 Thermal equilibrium Water (H2O), 10 in stars, 19, 601 discovery of in space, 135 Thermal instability, 39 maser emission from, 154, 157, 489, 506 Thermal jets, see Jets production in shocks, 154, 232, 233 Thermal relaxation, of intermediate-mass stars, 696 rotational states, 154 Thomson cross section, 819 sublimation of ice mantles, 53 Threshold density, for star formation, 736, 740 Wave action, 460 Toomre Q-parameter, 344, 740 Weak-lined T Tauri stars, defined, 98 Total extinction, defined, 44 Weber-Davis model, 466, 467 Trumpler, J., 11, 117 Werner band of H2, 145, 225, 523 Turbulence White dwarfs, 24 as source of line broadening, 806 in the HR diagram, 18 in magnetized gas, 279, 299 Wien’s displacement law, 50 Winds, see also Centrifugal winds; Solar wind; Ultracompact HII regions Weber-Davis model lifetime problem, 532 from Herbig Ae/Be stars, 710 OH masers near, 507 from high-mass stars, 10, 29 radio emission from, 532 from post-main-sequence stars, 24, 29 relation to giant molecular clouds, 115 from pre-main-sequence stars, 15 Ultracompact HII regions, defined, 115 optical and radio emission from high-mass Ultraluminous infrared galaxies, 753 stars, 540 Ultraviolet emission, from T Tauri stars, 631 radiative acceleration of, 537 UX Ori stars, 693 thermal acceleration of, 457 types of, 456 van Rhijn, P. J., 122 X-rays from, see X-rays Veiling index, defined, 632 Wolf-Rayet stars, 745 Veiling, of T Tauri absorption lines, 624, 630 in starburst irregular galaxies, 750 origin of, 645 Velocity dispersion Work function, 193 of cloud clumps, 64 Working surface, see Jets of HI clouds in the Milky Way, 32, 42 of molecular gas in the Milky Way, 34 X-factor, 170, 754 of stars in T associations, 99 X-ray emission, see Weak-lined T Tauri stars within dense cores, 74 X-rays within giant molecular clouds, 72 as heating sources of molecular clouds, 195 within OB associations, 107 emitted by winds from high-mass stars, 542 Vibrational temperature, 226 from Herbig Ae/Be stars, 714 Virial equilibrium, 71 from protostars, 322, 329 Virial theorem, 69, 802 from T Tauri stars, 636 Virial velocity, 72 from the , 636 Viscosity, 343 in local radiation field, 192, 567 852 Subject Index

saturation, in rotating stars, 621 of stellar absorption lines, 664 stellar, decline with age of, 672 of stellar spectral lines, 620 X-type neutral point, 303 Zero-age main sequence (ZAMS) approach to, 601 YY Orionis stars, 644 at low , 120 effect of metallicity on, 120 Zeeman splitting in maser sources, 493 establishment by main-sequence fitting, 118 of dark cloud emission, 80 Zero-age main sequence (ZAMS), defined, 22 of HI and OH, 71, 176, 257 Zone of avoidance, 62