Chemical analysis of prestellar cores in Ophiuchus yields short timescales and rapid collapse

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Table 4

Properties of the synthetic cores calculated at t_age, i.e. at the minimum o-H₂D⁺/p-D₂H⁺.

#	log₁₀ [n_core (t_form)]	M_core	log₁₀ [n_core (t_age)]	o-H₂ D⁺/p-D₂ H⁺		α	x(o-H₂D⁺)	x(p-D₂H⁺)	t_form	t_age
Core	(cm⁻³)	(M_⊙)	(cm⁻³)				log₁₀	log₁₀	(kyr)	(kyr)	(kyr)		(kyr)
F1_0035_1	5.79	1.06	6.11	1.19	0.69	1.23	−9.34	−9.42	44	132	42	3.1	640
F1_0035_2	5.79	1.15	6.14	0.94	0.71	1.17	−9.42	−9.40	44	215	42	5.0	649
F1_0035_OPR_1	5.79	1.33	6.21	0.79	0.91	1.31	−9.94	−9.84	44	166	42	3.9	392
F1_0035_OPR_2	5.79	0.97	6.07	1.57	0.71	1.38	−9.82	−10.02	44	176	42	4.1	397
F1_01_1	5.79	1.33	6.21	0.94	0.91	1.32	−9.75	−9.72	44	166	42	3.9	584
F1_01_2	5.79	1.00	6.08	3.18	0.70	1.33	−9.66	−10.17	44	185	42	4.3	590
F2_01_1	5.74	1.06	6.11	2.22	1.26	1.92	−9.43	−9.77	213	102	45	2.2	545
F2_01_2	5.70	0.62	5.88	2.63	0.42	1.38	−9.36	−9.78	249	75	47	1.6	571
F2_01_3	5.70	0.84	6.00	2.66	0.91	1.39	−9.46	−9.89	196	108	47	2.3	561
F2_01_4	5.70	0.57	5.84	3.74	0.31	0.98	−9.38	−9.96	256	69	47	1.5	550
F2_01_5	5.70	0.73	5.95	2.40	0.37	0.81	−9.37	−9.76	223	102	47	2.1	549
F3_01_1	5.74	0.66	5.90	1.84	0.51	1.05	−9.44	−9.70	294	36	45	0.8	1057
F3_01_2	5.74	0.69	5.92	1.46	0.98	1.83	−9.70	−9.86	245	65	45	1.4	453
F3_01_3	5.74	0.65	5.90	1.73	0.56	1.13	−9.50	−9.74	278	52	45	1.1	801
F3_01_4	5.71	0.49	5.77	2.24	0.55	1.51	−9.42	−9.77	307	24	46	0.5	1295
F3_01_5	5.74	0.63	5.88	1.76	0.89	1.78	−9.50	−9.75	282	43	45	0.9	539

Notes. The properties were calculated by assuming an R_eq = 0.02 pc, which is an average of the effective size of the observed cores. We report the core mass M_core, volume density n_core (t_age), ortho-to-para ratio, Mach number (), and virial parameter (α). We also report the abundances of o-H₂ D⁺ and p-D₂ H⁺, and the relevant timescales: the core formation time, t_form, i.e. the time at which the core is formed, the core age t_age, the free-fall time calculated at the n_core(t_form), the ratio between the age and the dynamical time , which gives an idea on the collapse speed, and the ambipolar diffusion time calculated by taking the electron fraction at the core formation time t_form.

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