Seminars at FGG
The unprecedented NIRSpec@JWST view of the nuclear region in the prototypical merging galaxy NGC 6240
Speaker: Matteo Ceci (INAF - Osservatorio di Arcetri (Firenze, Italy))
Date and time: 2024-06-06 12:30
Merger events are thought to be a fundamental evolutionary phase in massive galaxies assembly. At the same time, Active Galactic Nuclei (AGN) play a fundamental role in the evolution of galaxies. Both phenomena can be observed at work in the active merging galaxy NGC 6240, the subject of my study. NGC 6240 is indeed considered the prototypical merger galaxy in the local universe. Having an elevated IR luminosity, it is classified as an UltraLuminous InfraRed Galaxy (ULIRG). It hosts two AGN, positioned approximately 735 parsecs (1.5 arcsec) apart, observed both in X-ray and radio bands. Thanks to the unrivalled observations offered by NIRSpec@JWST, we investigated the nuclear region (3" × 3") of this galaxy, observing the gas kinematics and ISM properties with unprecedented spatial resolution and sensitivity. We studied the ISM properties with the most used NIR diagnostics methods. We isolated the ionization cones of the two nuclei and we found that the molecular hydrogen lines are dominated by thermal emission. We computed the molecular and ionized gas mass present in our field of view, finding values in according with those in the literature. We discovered that the molecular hydrogen has a different kinematics from the ionized gas. In particular, from the channel maps, we observed the complex kinematics of the warm molecular gas, finding kinematic features never seen before with this resolution, such as filaments connecting a redshifted cloud with the two nuclei and a blue outflow near the Southern nucleus. We focused our discussion on this highly redshifted blob of H2 and proposed two different scenarios for its nature: either a structure due to outflowing gas or a tidal cloud inflowing on the nuclei.