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Table 2

H2 observed line intensities, populations in each upper level, rotational excitation temperatures, ortho-to-para ratio, and column densities.

Source I 0−0   S(0)a I 0−0   S(1)a I 0−0   S(2)a I 0−0   S(3)a I 1−0   S(1)a Ref.
(erg s-1 cm-2 sr-1) (erg s-1 cm-2 sr-1) (erg s-1 cm-2 sr-1) (erg s-1 cm-2 sr-1) (erg s-1 cm-2 sr-1)

L1721 6.9e–06[1.5e–06] 2.3e–05[1.1e–06] 9.1e–06[2.6e–06]  < 1.0e–05 (1)
California 4.6e–06[7.0e–07] 1.3e–05[1.3e–06] 6.4e–06[3.2e–06] 5.5e–06[2.7e–06] (1)
N7023E 3.0e–05[1.3e–06] 1.5e–04[1.1e–05] 1.5e–04[2.0e–05] 9.2e–05[4.6e–05] (1)
Horsehead 1.2e–05[2.8e–06] 4.3e–05[9.4e–06] 5.4e–05[1.3e–05] 5.9e–05[1.3e–05] 7.5e–06[1.5e–06] (1, 2)
rho Oph 6.6e–05[1.4e–05] 2.5e–04[5.5e–05] 2.4e–04[4.8e–05] 8.6e–05[8.6e–06] 2.3e–05[5.7e–06] (1, 2)
N2023N 5.5e–05[1.2e–05] 1.5e–04[3.2e–05] 1.1e–04[4.0e–05] 6.2e–05[3.1e–05] 1.1e–05[2.2e–06] (1, 2)
Source N (0,2)b N (0,3)b N (0,4)b N (0,5)b N (1,3)b
(cm-2) (cm-2) (cm-2) (cm-2) (cm-2)

L1721 4.2e+19[9.4e+18] 5.2e+18[2.5e+17] 2.6e+17[7.3e+16]  < 6.2e+16 0.007[0.002]
California 2.8e+19[4.2e+18] 3.0e+18[2.9e+17] 1.8e+17[9.1e+16] 3.4e+16[1.7e+16] 0.007[0.004]
N7023E 1.8e+20[8.1e+18] 3.4e+19[2.6e+18] 4.2e+18[5.7e+17] 5.7e+17[2.8e+17] 0.022[0.003]
Horsehead 7.1e+19[1.7e+19] 9.8e+18[2.1e+18] 1.5e+18[3.8e+17] 3.7e+17[8.3e+16] 1.0e+15[2.0e+14] 0.023[0.008]
rho Oph 4.0e+20[8.6e+19] 5.8e+19[1.2e+19] 6.9e+18[1.3e+18] 5.4e+17[5.4e+16] 3.0e+15[7.7e+14] 0.016[0.005]
N2023N 3.3e+20[7.3e+19] 3.5e+19[7.2e+18] 3.0e+18[1.1e+18] 3.8e+17[1.9e+17] 1.9e+15[3.7e+14] 0.009[0.004]
Source T 42c T53c T64c T 75 c OTP53d OTP75d
(K) (K) (K) (K)

L1721 206.[ 19.]  < 305.
California 208.[ 25.] 301.[ 38.] 2.3
N7023E 269.[ 11.] 327.[ 43.] 1.3
Horsehead 264.[ 30.] 398.[ 49.] 458.[ 92.] 747.[208.] 1.5 2.7
rho Oph 252.[ 22.] 290.[ 18.] 327.[ 20.] 543.[ 48.] 1.1 2.6
N2023N 221.[ 26.] 300.[ 45.] 1.6
Source N(H2)42e N(H2)53e N(H2)64e N(H2)75e
(cm-2) (cm-2) (cm-2) (cm-2)

L1721 4.9e+20 5.1e+19
California 3.2e+20 3.0e+19
N7023E 1.5e+21 2.9e+20
Horsehead 6.1e+20 5.7e+19 7.5e+19 6.0e+18
rho Oph 3.6e+21 6.4e+20 1.1e+21 2.3e+19
N2023N 3.5e+21 3.5e+20



Intensities at the emission peak with uncertainty (1σ) between brackets.


The level populations N(vuJ) are derived under the assumption that the line is optically thin.


Excitation rotational temperature, TJ2J1, derived from the ratio of the N(0, J2) and N(0, J1) column densities.


Fit of the ortho-to-para (OTP) ratio of the J1 − J2 levels and assuming thermalized emission at the temperature TJ2J1.


The total H2 column density inferred from the N(0, J1) column densities assuming optically thin, thermalized emission at the temperature TJ2J1.

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