Oral Presentation

Massive molecular gas companions uncovered by VLA CO(1–0) observations of the z = 5.2 radio galaxy TN J0924−2201

Author(s): Kianhong Lee (University of Tokyo/NAOJ)

Presenter: Kianhong Lee (University of Tokyo/NAOJ)

We present Karl G. Jansky Very Large Array (VLA) K-band (19 GHz) observations of the redshifted CO(1–0) line emission toward the radio galaxy TN J0924−2201 at z = 5.2, which is one of the most distant CO-detected radio galaxies. With the angular resolution of ∼ 2′′, the CO(1–0) line emission is resolved into three clumps, within ±500 km s−1 relative to its redshift, where is determined by Lyα. We find that they locate off-center and 12–33 kpc away from the center of the host galaxy, which has counterparts in HST i-band, Spitzer/IRAC and ALMA Band-6 (230 GHz; 1.3 mm). With the ALMA detection, we estimate LIR and SFR of the host galaxy to be (9.3 ± 1.7) × 10^11 L⊙ and 110 ± 20 M⊙ yr−1, respectively. We also derive the 3σ upper limit of MH2< 1.3 × 10^10 M⊙ at the host galaxy. The detected CO(1–0) line luminosities of three clumps, L′CO(1−0) = (3.2–4.7)×10^11 Kkms−1pc2, indicate the presence of three massive molecular gas reservoirs with MH2 = (2.5–3.7)×10^10 M⊙, by assuming the CO-to-H2 conversion factor αCO = 0.8 M⊙ (K km s−1pc2)−1, although the star formation rate (SFR) is not elevated because of the non-detection of ALMA 1.3 mm continuum (SFR < 40 M⊙ yr−1). From the host galaxy, the nearest molecular gas clump labeled as clump A, is apparently aligning with the radio jet axis, showing the radio-CO alignment. The possible origin of these three clumps around TN J0924–2201 can be interpreted as merger, jet-induced metal enrichment and outflow.