Table 2: AFGL 2591 predicted column densities (cm^-2) for different X-ray models.
Model 2 Model 3 Model 4 Model 6

Species $N_{{\rm beam}}$ q_2/0 q_2/1 $N_{{\rm beam}}$ q_3/0 q_3/1 $N_{{\rm beam}}$ q_4/0 q_4/1 $N_{{\rm beam}}$

H 3.1E+16 1.9 0.1 1.7E+17 10.6 0.6 1.6E+18 96.5 5.2 1.4E+18

C 7.5E+13 5.4 2.0E-02 5.2E+14 37.2 0.1 3.2E+15 228.9 0.7 6.0E+15

N 8.3E+15 7.0 2.0 1.0E+17 84.9 24.8 1.7E+17 145.4 42.4 1.7E+17

O 3.6E+17 8.4 7.2 2.2E+18 50.2 43.6 2.4E+18 55.8 48.4 2.4E+18

S 4.1E+14 1.0 1.1 3.2E+15 7.9 8.2 1.5E+16 36.2 37.6 1.3E+16

CH 2.0E+11 0.4 0.2 1.9E+11 0.4 0.2 7.4E+12 16.8 6.5 4.7E+12

NH 4.0E+12 0.5 0.5 2.2E+12 0.3 0.3 7.4E+12 0.9 0.9 4.8E+12

NH₂ 1.6E+13 0.9 1.1 1.2E+13 0.7 0.8 4.0E+13 2.2 2.7 2.4E+13

OH 8.8E+14 0.4 0.4 2.0E+14 0.1 0.1 1.4E+15 0.7 0.6 1.2E+15

HCN 3.5E+15 9.3 0.8 6.0E+15 15.9 1.4 1.1E+15 2.9 0.2 1.7E+15

CN 3.9E+11 1.5 3.0E-02 2.5E+12 9.5 0.2 1.3E+13 50.0 1.1 2.1E+13

HNC 8.9E+14 6.0 7.3 1.1E+15 7.2 8.7 2.8E+14 1.9 2.3 2.7E+14

N₂O 5.1E+12 1.7 1.7 1.9E+13 6.3 6.1 7.5E+13 24.8 24.2 6.7E+13

NO 4.4E+15 0.6 0.6 6.8E+14 0.1 0.1 3.4E+15 0.5 0.5 2.7E+15

HNO 3.7E+12 1.2 1.2 4.5E+12 1.5 1.5 3.3E+13 10.9 10.9 2.4E+13

SH 8.3E+11 0.8 0.5 6.0E+11 0.6 0.4 3.6E+12 3.3 2.2 2.7E+12

H₂S 7.0E+10 0.3 0.4 1.3E+12 5.8 6.8 3.3E+12 14.9 17.5 3.3E+12

SO 5.3E+15 6.7 6.6 2.0E+16 25.3 24.7 9.4E+15 12.0 11.7 1.1E+16

CS 4.2E+13 1.5 0.8 3.2E+14 11.6 6.2 1.4E+15 51.1 27.1 1.2E+15

H⁺ 2.2E+11 14.1 14.1 4.4E+12 278.9 278.2 4.7E+13 2995.3 2988.0 3.4E+13

He⁺ 1.1E+11 2.1 2.1 6.8E+11 12.5 12.5 6.4E+12 117.7 117.7 4.6E+12

C⁺ 5.5E+11 5.0 0.1 1.0E+13 93.4 2.5 1.1E+14 982.8 26.3 8.0E+13

N⁺ 1.4E+07 2.0 2.0 7.9E+07 11.3 11.3 7.3E+08 103.4 103.5 5.2E+08

O⁺ 1.7E+07 7.0 2.2 1.6E+08 65.8 20.8 1.5E+09 631.7 199.2 1.1E+09

S⁺ 1.2E+11 8.2 1.0E-02 4.2E+12 294.1 0.5 1.1E+14 7454.9 13.1 7.8E+13

H₃⁺ 1.2E+12 2.9 2.9 6.9E+12 17.0 17.0 6.4E+13 158.4 158.4 4.6E+13

H₃O⁺ 4.0E+13 1.2 1.1 3.6E+13 1.0 1.0 9.2E+13 2.7 2.5 7.9E+13

OH⁺ 5.3E+07 8.9 3.5 9.8E+08 164.2 65.2 9.8E+09 1648.7 654.7 7.0E+09

CH⁺ 9.0E+04 28.3 4.0E-04 6.3E+06 1973.4 3.0E-04 2.9E+08 9.0E+04 1.2 4.9E+08

CO⁺ 1.4E+07 3.1 1.1 5.9E+07 13.0 4.4 5.0E+08 109.3 36.7 3.7E+08

HCO⁺ 4.5E+13 25.8 9.9 3.4E+14 193.0 74.0 1.4E+15 783.3 300.5 1.2E+15

HOC⁺ 1.9E+07 1.4 2.0E-02 7.9E+07 5.5 0.1 7.8E+08 54.5 0.9 1.4E+09

HCNH⁺ 4.3E+12 5.6 1.2 9.7E+12 12.8 2.8 8.4E+12 11.1 2.4 9.7E+12

N₂H⁺ 3.7E+11 3.8 3.8 2.2E+12 22.7 22.7 1.8E+13 189.9 190.1 1.3E+13

HCS⁺ 3.7E+10 5.1 0.4 1.0E+12 135.1 10.9 1.0E+13 1349.3 108.7 7.8E+12

SO⁺ 3.5E+11 4.4 1.4 3.1E+12 38.9 12.6 9.2E+12 116.4 37.8 8.6E+12

HSO⁺ 6.4E+12 145.2 143.2 3.4E+13 766.1 755.6 1.9E+13 423.9 418.1 2.2E+13

SH⁺ 3.0E+09 38.1 2.4 2.7E+11 3494.5 218.6 3.9E+12 5.0E+04 3104.7 3.0E+12

The beam averaged column densities $N_{{\rm beam}}$ are calculated for a 2 $^{\prime \prime }$ beam ( $\approx$ 2000 AU). The enhancement factor q_x/y is defined by $N_{i,{\rm Model}~x}/N_{i,{\rm Model}~y}$ . Model 0 is the model without any inner radiation field, model 1 has no X-rays but an inner FUV field ( $G_{{\rm0,in}} = 10$ ). Models 2-4 are X-ray models with log( $L_{{\rm X}}) = 29$ , 30 and 31, respectively. Model 6 is one of the best fitted models with an inner FUV field $G_{{\rm0,in}} = 10$ , $L_{{\rm X}} = 8 \times 10^{31}$ erg s^-1, $T_{{\rm X}} = 10^8$ K and $N_{{\rm H,in}} = 3 \times 10^{22}$ cm^-2.

**Table 2:** AFGL 2591 predicted column densities (cm^-2) for different X-ray models.
	Model 2			Model 3			Model 4			Model 6
Species	$N_{{\rm beam}}$	q_2/0	q_2/1	$N_{{\rm beam}}$	q_3/0	q_3/1	$N_{{\rm beam}}$	q_4/0	q_4/1	$N_{{\rm beam}}$
H	3.1E+16	1.9	0.1	1.7E+17	10.6	0.6	1.6E+18	96.5	5.2	1.4E+18
C	7.5E+13	5.4	2.0E-02	5.2E+14	37.2	0.1	3.2E+15	228.9	0.7	6.0E+15
N	8.3E+15	7.0	2.0	1.0E+17	84.9	24.8	1.7E+17	145.4	42.4	1.7E+17
O	3.6E+17	8.4	7.2	2.2E+18	50.2	43.6	2.4E+18	55.8	48.4	2.4E+18
S	4.1E+14	1.0	1.1	3.2E+15	7.9	8.2	1.5E+16	36.2	37.6	1.3E+16
CH	2.0E+11	0.4	0.2	1.9E+11	0.4	0.2	7.4E+12	16.8	6.5	4.7E+12
NH	4.0E+12	0.5	0.5	2.2E+12	0.3	0.3	7.4E+12	0.9	0.9	4.8E+12
NH₂	1.6E+13	0.9	1.1	1.2E+13	0.7	0.8	4.0E+13	2.2	2.7	2.4E+13
OH	8.8E+14	0.4	0.4	2.0E+14	0.1	0.1	1.4E+15	0.7	0.6	1.2E+15
HCN	3.5E+15	9.3	0.8	6.0E+15	15.9	1.4	1.1E+15	2.9	0.2	1.7E+15
CN	3.9E+11	1.5	3.0E-02	2.5E+12	9.5	0.2	1.3E+13	50.0	1.1	2.1E+13
HNC	8.9E+14	6.0	7.3	1.1E+15	7.2	8.7	2.8E+14	1.9	2.3	2.7E+14
N₂O	5.1E+12	1.7	1.7	1.9E+13	6.3	6.1	7.5E+13	24.8	24.2	6.7E+13
NO	4.4E+15	0.6	0.6	6.8E+14	0.1	0.1	3.4E+15	0.5	0.5	2.7E+15
HNO	3.7E+12	1.2	1.2	4.5E+12	1.5	1.5	3.3E+13	10.9	10.9	2.4E+13
SH	8.3E+11	0.8	0.5	6.0E+11	0.6	0.4	3.6E+12	3.3	2.2	2.7E+12
H₂S	7.0E+10	0.3	0.4	1.3E+12	5.8	6.8	3.3E+12	14.9	17.5	3.3E+12
SO	5.3E+15	6.7	6.6	2.0E+16	25.3	24.7	9.4E+15	12.0	11.7	1.1E+16
CS	4.2E+13	1.5	0.8	3.2E+14	11.6	6.2	1.4E+15	51.1	27.1	1.2E+15
H⁺	2.2E+11	14.1	14.1	4.4E+12	278.9	278.2	4.7E+13	2995.3	2988.0	3.4E+13
He⁺	1.1E+11	2.1	2.1	6.8E+11	12.5	12.5	6.4E+12	117.7	117.7	4.6E+12
C⁺	5.5E+11	5.0	0.1	1.0E+13	93.4	2.5	1.1E+14	982.8	26.3	8.0E+13
N⁺	1.4E+07	2.0	2.0	7.9E+07	11.3	11.3	7.3E+08	103.4	103.5	5.2E+08
O⁺	1.7E+07	7.0	2.2	1.6E+08	65.8	20.8	1.5E+09	631.7	199.2	1.1E+09
S⁺	1.2E+11	8.2	1.0E-02	4.2E+12	294.1	0.5	1.1E+14	7454.9	13.1	7.8E+13
H₃⁺	1.2E+12	2.9	2.9	6.9E+12	17.0	17.0	6.4E+13	158.4	158.4	4.6E+13
H₃O⁺	4.0E+13	1.2	1.1	3.6E+13	1.0	1.0	9.2E+13	2.7	2.5	7.9E+13
OH⁺	5.3E+07	8.9	3.5	9.8E+08	164.2	65.2	9.8E+09	1648.7	654.7	7.0E+09
CH⁺	9.0E+04	28.3	4.0E-04	6.3E+06	1973.4	3.0E-04	2.9E+08	9.0E+04	1.2	4.9E+08
CO⁺	1.4E+07	3.1	1.1	5.9E+07	13.0	4.4	5.0E+08	109.3	36.7	3.7E+08
HCO⁺	4.5E+13	25.8	9.9	3.4E+14	193.0	74.0	1.4E+15	783.3	300.5	1.2E+15
HOC⁺	1.9E+07	1.4	2.0E-02	7.9E+07	5.5	0.1	7.8E+08	54.5	0.9	1.4E+09
HCNH⁺	4.3E+12	5.6	1.2	9.7E+12	12.8	2.8	8.4E+12	11.1	2.4	9.7E+12
N₂H⁺	3.7E+11	3.8	3.8	2.2E+12	22.7	22.7	1.8E+13	189.9	190.1	1.3E+13
HCS⁺	3.7E+10	5.1	0.4	1.0E+12	135.1	10.9	1.0E+13	1349.3	108.7	7.8E+12
SO⁺	3.5E+11	4.4	1.4	3.1E+12	38.9	12.6	9.2E+12	116.4	37.8	8.6E+12
HSO⁺	6.4E+12	145.2	143.2	3.4E+13	766.1	755.6	1.9E+13	423.9	418.1	2.2E+13
SH⁺	3.0E+09	38.1	2.4	2.7E+11	3494.5	218.6	3.9E+12	5.0E+04	3104.7	3.0E+12

Source LaTeX | All tables | In the text

	1 Introduction
	2 Model
	3 X-ray induced chemistry
	4 Results and discussion
	5 X-ray tracers
	6 AFGL 2591 models
	7 Calculated emission lines
	8 Conclusion
	References
	Online Material
	Appendix A: Initial chemical abundances
	Appendix B: Electron recombination and charge transfer reactions
	Appendix C: Influence of $T{_{{\rm X}}}$ and $N{_{{\rm H,in}}}$
	Appendix D: Influence of an outer FUV field and cosmic rays
	Appendix E: Comparison to observations