Absorption of Millimeter-band CO and CN in the Early Universe: Molecular Clouds in the Radio Galaxy B2 0902+34 at Redshift 3.4

• DOI: 10.3847/1538-4357/ad198d
• Publication Date: 2024-02-20T16:42:56Z
• Authors: Bjorn H. C. Emonts; Steve J. Curran; George K. Miley; Matthew D. Lehnert; Chris L. Carilli; Ilsang Yoon; Raffaella Morganti; Reinout J. van We...; Montserrat Villar...; Pierre Guillard; Cristina M. Cordun; Tom A. Oosteroo
• Keywords: QB460-466; Galaxy jets; Radio sources; Cosmological parameters; Quasar absorption line spectroscopy; Extinction; [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph]; [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]; Astrophysics; Astrophysics - Astrophysics of Galaxies; Radio spectroscopy; Astrophysics - Cosmology and Nongalactic Astrophysics

Abstract Using the Karl G. Jansky Very Large Array, we have detected absorption lines due to carbon monoxide, CO( J = 0 → 1), and cyano radical, CN( N associated with radio galaxy B2 0902+34 at redshift z 3.4. The detection of millimeter-band observed 1.5 Gyr after Big Bang facilitates studying molecular clouds down gas masses inaccessible emission-line observations. CO in has a peak optical depth τ ≥ 8.6% consists two components, one which same as previously 21 cm neutral hydrogen (H i ) gas. Each component traces an integrated H 2 column density <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:math> ≳ 3 × 10 20 −2 . CN is for both well blueshifted not CO, CO/CN line ratios ranging from ≲0.4 2.4. We discuss scenario that components originate collections small dense are embedded region more diffuse high turbulence, possibly within influence central active galactic nucleus or starburst region. degree reddening 0902+34, rest-frame color B − K ∼ 4.2, lower than very red colors ( &gt; 6) found among other known redshifted systems &lt; 1. Nevertheless, when including many nondetections literature, potential correlation between absorption-line strength evident, giving weight argument absorbers dust content.