JWST detection of extremely excited outflowing CO and H₂O in VV 114 E SW: A possible rapidly accreting IMBH

Abstract

Mid-infrared (mid-IR) gas-phase molecular bands are powerful diagnostics of the warm interstellar medium. We report the James Webb Space Telescope detection of the CO v = 1 − 0 (4.4 − 5.0 μm) and H 2 O ν 2 = 1 − 0 (5.0 − 7.8 μm) ro-vibrational bands, both in absorption, toward the “s2” core in the southwest nucleus of the merging galaxy VV 114 E. All ro-vibrational CO lines up to J low = 33 ( E low ≈ 3000 K) are detected, as well as a forest of H 2 O lines up to 13 0, 13 ( E low ≈ 2600 K). The highest-excitation lines are blueshifted by ∼180 km s −1 relative to the extended molecular cloud, which is traced by the rotational CO ( J = 3 − 2) 346 GHz line observed with the Atacama Large Millimeter/submillimeter Array. The bands also show absorption in a low-velocity component (blueshifted by ≈30 km s −1 ) with lower excitation. The analysis shows that the bands are observed against a continuum with an effective temperature of T bck ∼ 550 K extinguished with τ 6 μm ext ∼ 2.5 −3 ( A k ∼ 6.9 − 8.3 mag). The high-excitation CO and H 2 O lines are consistent with v = 0 thermalization with T rot ≈ 450 K and column densities of N CO ≈ (1.7 − 3.5)×10 19 cm −2 and N H 2 O ≈ (1.5 − 3.0)×10 19 cm −2 . Thermalization of the v = 0 levels of H 2 O requires either an extreme density of n H 2 ≳ 10 9 cm −3 , or radiative excitation by the mid-IR field in a very compact (< 1 pc) optically thick source emitting ∼10 10 L ⊙ . The latter alternative is favored, implying that the observed absorption probes the very early stages of a fully enshrouded active black hole (BH). On the basis of a simple model for BH growth and applying a lifetime constraint to the s2 core, an intermediate-mass BH (IMBH, M BH ∼ 4.5 × 10 4 M ⊙ ) accreting at super-Eddington rates is suggested, where the observed feedback has not yet been able to break through the natal cocoon.

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