2024A&A...688A.118L

Context. Molecular deuteration is commonly seen in starless cores and is expected to occur on a timescale comparable to that of the core contraction. Thus, the deuteration serves as a chemical clock, allowing us to investigate dynamical theories of core formation.
Aims. We aim to provide a 3D cloud description for the starless core L 1498 located in the nearby low-mass star-forming region Taurus and explore its possible core formation mechanism.
Methods. We carried out nonlocal thermal equilibrium radiative transfer with multi-transition observations of the high-density tracer N₂H⁺ to derive the density and temperature profiles of the L 1498 core. By combining these observations with the spectral observations of the deuterated species, ortho-H₂D⁺, N₂D⁺, and DCO⁺, we derived the abundance profiles for the observed species and performed chemical modeling of the deuteration profiles across L 1498 to constrain the contraction timescale.
Results. We present the first ortho-H₂D⁺ (1₁₀-1₁₁) detection toward L 1498. We find a peak molecular hydrogen density of 1.6_–0.3^+3.0 × 10⁵ cm^–3, a temperature of 7.5_–0.5^+0.7 K, and a N₂H⁺ deuteration of 0.27_–0.15^+0.12 in the center.
Conclusions. We derived a lower limit of the core age for L 1498 of 0.16 Ma, which is compatible with the typical free-fall time, indicating that L 1498 likely formed rapidly.