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 H2O ν2 = 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 Jlow = 33 (Elow ≈ 3000 K) are detected, as well as a forest of H2O lines up to 130,13 (Elow ≈ 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 Tbck ∼ 550 K extinguished with τext6 µm ∼ 2.5-3 (Ak ∼ 6.9-8.3 mag). The high-excitation CO and H2O lines are consistent with v = 0 thermalization with Trot ≈ 450 K and column densities of NCO ≈ (1.7-3.5) × 1019 cm-2 and NH2O ≈ (1.5-3.0) × 1019 cm-2. Thermalization of the v = 0 levels of H2O requires either an extreme density of nH2 & 109 cm-3, or radiative excitation by the mid-IR field in a very compact (<1 pc) optically thick source emitting ∼1010 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, MBH ∼ 4.5×104 M ) accreting at super-Eddington rates is suggested, where the observed feedback has not yet been able to break through the natal cocoon.