MIDINFRARED ROTATIONAL LINE EMISSION FROM INTERSTELLAR MOLECULAR-HYDROGEN

被引:129
作者
BURTON, MG [1 ]
HOLLENBACH, DJ [1 ]
TIELENS, AGGM [1 ]
机构
[1] NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035
关键词
INFRARED; INTERSTELLAR; LINES; ISM; MOLECULES; MOLECULAR PROCESSES; SHOCK WAVES;
D O I
10.1086/171947
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We have modeled the line emission from the v = 0-0 S(O), S(2), and S(3), and the v = 1-0 and v = 2-1 S(1) transitions of molecular hydrogen in clouds exposed to high far-ultraviolet fluxes (i.e., photodissociation regions or PDRs) and in shocks. In particular, we have studied the lowest pure rotational H-2 transitions [the 0-0 S(0) and 0-0 S(1) lines], at 28 and 17 mum, respectively. We find that, in PDRs, the emission comes from warm (T greater than or similar to 100 K) molecular gas, situated at optical depths A(v) greater than or similar to 1, beyond the hot atomic surface layer of the clouds. For FUV fields, G0 = 10(3)-10(5) times the average interstellar field and densities n = 10(3)-10(7) CM-3, the typical line intensities are in the range 10(-6) to 10(-4) ergs s-1 cm-2 sr-1. We compare the predictions for the line intensities from both C-type and J-type shock models. For both nondissociative and dissociative molecular shocks, in the same density range, the line intensities range from 10(-6) to 10(-3) ergs s-1 cm-2 sr-1. In the faster, dissociative shocks (v(s) greater than or similar to 25-30 km s-1), the H-2 line emission arises from reformed molecules, downstream of the shock front. Shocked line emission may be detectable from lower velocity shocks (i.e., v(s) approximately 5 km s-1) than previously observed. Measurements of the relative line ratios may be used to help discriminate between competing models for the shock excitation of molecular gas. Observations of these lines will also provide a powerful probe of the extensive regions of warm molecular gas in the Galaxy. The results are applied to recent observations of the 0-0 S(1) transition in both the PDR and the shocked ps in Orion. The Infrared Satellite Observatory (ISO) should detect the v = 0-0 low-J transitions in numerous active regions.
引用
收藏
页码:563 / 572
页数:10
相关论文
共 37 条
  • [1] INFRARED STUDIES OF AN IONIZATION FRONT REGION IN ORION NEBULA
    BECKLIN, EE
    BECKWITH, S
    GATLEY, I
    MATTHEWS, K
    NEUGEBAUER, G
    SARAZIN, C
    WERNER, MW
    [J]. ASTROPHYSICAL JOURNAL, 1976, 207 (03) : 770 - &
  • [2] OBSERVATIONS OF MOLECULAR-HYDROGEN EMISSION FROM ORION NEBULA
    BECKWITH, S
    PERSSON, SE
    NEUGEBAUER, G
    BECKLIN, EE
    [J]. ASTROPHYSICAL JOURNAL, 1978, 223 (02) : 464 - 470
  • [3] FLUORESCENT EXCITATION OF INTERSTELLAR H2
    BLACK, JH
    VANDISHOECK, EF
    [J]. ASTROPHYSICAL JOURNAL, 1987, 322 (01) : 412 - 449
  • [4] RATIOS OF MOLECULAR-HYDROGEN LINE-INTENSITIES IN SHOCKED GAS - EVIDENCE FOR COOLING ZONES
    BRAND, PWJL
    MOORHOUSE, A
    BURTON, MG
    GEBALLE, TR
    BIRD, M
    WADE, R
    [J]. ASTROPHYSICAL JOURNAL, 1988, 334 (02) : L103 - L106
  • [5] THE CONSTANCY OF THE RATIO OF THE MOLECULAR-HYDROGEN LINES AT 3.8-MU-M IN ORION
    BRAND, PWJL
    TONER, MP
    GEBALLE, TR
    WEBSTER, AS
    WILLIAMS, PM
    BURTON, MG
    [J]. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1989, 236 (04) : 929 - 934
  • [6] SHOCKED MOLECULAR-HYDROGEN IN THE SUPERNOVA REMNANT IC-443
    BURTON, MG
    GEBALLE, TR
    BRAND, PWJL
    WEBSTER, AS
    [J]. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1988, 231 (03) : 617 - &
  • [7] SHOCKED [O-I] 63 MICRON LINE EMISSION FROM THE SUPERNOVA REMNANT IC-443
    BURTON, MG
    HOLLENBACH, DJ
    HAAS, MR
    ERICKSON, EF
    [J]. ASTROPHYSICAL JOURNAL, 1990, 355 (01) : 197 - 209
  • [8] LINE EMISSION FROM CLUMPY PHOTODISSOCIATION REGIONS
    BURTON, MG
    HOLLENBACH, DJ
    TIELENS, AGGM
    [J]. ASTROPHYSICAL JOURNAL, 1990, 365 (02) : 620 - 639
  • [9] MOLECULAR-HYDROGEN LINE RATIOS IN 4 REGIONS OF SHOCK-EXCITED GAS
    BURTON, MG
    BRAND, PWJL
    GEBALLE, TR
    WEBSTER, AS
    [J]. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1989, 236 (02) : 409 - 423
  • [10] BURTON MG, 1989, ESA SP290, P281