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

ASTRONOMY & ASTROPHYSICS(2024)

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摘要
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 mu m) and H2O nu2 = 1 - 0 (5.0 - 7.8 mu m) 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 approximate to 3000 K) are detected, as well as a forest of H2O lines up to 130, 13 (Elow approximate to 2600 K). The highest-excitation lines are blueshifted by similar to 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 approximate to 30 km s-1) with lower excitation. The analysis shows that the bands are observed against a continuum with an effective temperature of Tbck similar to 550 K extinguished with tau6 mu mext similar to 2.5-3 (Ak similar to 6.9 - 8.3 mag). The high-excitation CO and H2O lines are consistent with v = 0 thermalization with Trot approximate to 450 K and column densities of NCO approximate to (1.7 - 3.5)x1019 cm-2 and NH2O approximate to (1.5 - 3.0)x1019 cm-2. Thermalization of the v = 0 levels of H2O requires either an extreme density of nH2 greater than or similar to 109 cm-3, or radiative excitation by the mid-IR field in a very compact (< 1 pc) optically thick source emitting similar to 1010 Lcircle dot. 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 similar to 4.5 x 104 Mcircle dot) 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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galaxies: evolution,galaxies: nuclei,infrared: galaxies
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