Details

Autor(en) / Beteiligte

• Emig, Kimberly L.
• Gupta, Neeraj
• Salas, Pedro
• Muller, Sébastien
• Balashev, Sergei A.
• Combes, Françoise
• Momjian, Emmanuel
• Song, Yiqing
• Jagannathan, Preshanth
• Deka, Partha P.
• Józsa, Gyula I. G.
• Klöckner, Hans-Rainer
• Mohapatra, Abhisek
• Noterdaeme, Pasquier
• Petitjean, Patrick
• Srianand, Raghunathan
• Wagenveld, Jonah D.

Titel

Discovery of Hydrogen Radio Recombination Lines at z = 0.89 toward PKS 1830-211

Ist Teil von

• The Astrophysical journal, 2023-02, Vol.944 (1), p.93

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2023

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Abstract We report the detection of stimulated hydrogen radio recombination line (RRL) emission from ionized gas in a z = 0.89 galaxy using 580–1670 MHz observations from the MeerKAT Absorption Line Survey. The RRL emission originates in a galaxy that intercepts and strongly lenses the radio blazar PKS 1830−211 ( z = 2.5). This is the second detection of RRLs outside of the local Universe and the first clearly associated with hydrogen. We detect effective H144 α (and H163 α ) transitions at observed frequencies of 1156 (798) MHz by stacking 17 (27) RRLs with 21 σ (14 σ ) significance. The RRL emission contains two main velocity components and is coincident in velocity with H i 21 cm and OH 18 cm absorption. We use the RRL spectral line energy distribution and a Bayesian analysis to constrain the density ( n e ) and the volume-averaged path length ( ℓ ) of the ionized gas. We determine log ( n e ) = 2.0 − 0.7 + 1.0 cm −3 and log ( ℓ ) = − 0.7 − 1.1 + 1.1 pc toward the northeast (NE) lensed image, likely tracing the diffuse thermal phase of the ionized ISM in a thin disk. Toward the southwest (SW) lensed image, we determine log ( n e ) = 3.2 − 1.0 + 0.4 cm −3 and log ( ℓ ) = − 2.7 − 0.2 + 1.8 pc, tracing gas that is more reminiscent of H scii regions. We estimate a star formation (surface density) rate of Σ SFR ∼ 0.6 M ⊙ yr −1 kpc −2 or SFR ∼ 50 M ⊙ yr −1 , consistent with a star-forming main-sequence galaxy of M ⋆ ∼ 10 11 M ⊙ . The discovery presented here opens up the possibility of studying ionized gas at high redshifts using RRL observations from current and future (e.g., SKA and ngVLA) radio facilities.