JWST/NIRSpec Reveals Diverse Nuclear Environments in Dwarf Galaxies Hosting Active Galactic Nuclei

Abstract

Dwarf galaxies, in the ΛCDM framework, are expected to dominate the galaxy number density at all redshifts. As such, studying active galactic nuclei (AGN) in these systems, including characterizing their local environments and emission properties, is essential in obtaining a comprehensive view of the AGN population and their influence on their host galaxy. To this end, we present James Webb Space Telescope (JWST)/NIRSpec IFU observations of four dwarf galaxies (M⋆ < 109.5 M⊙) with evidence of AGN activity. Utilizing the improvements in resolution and sensitivity offered by JWST, we investigate the emission features of the central kiloparsec of these dwarfs. Our findings include the detection of over 100 emission lines across our sample, including coronal lines with ionization potentials greater than 300 eV. The nuclear spectra show diverse emission features. In two galaxies, we measure strong contributions from hot dust to the infrared continuum. We also detect both polycyclic aromatic hydrocarbon (PAH) and coronal line emission within 100 pc of the nuclei in three galaxies. We estimate the hot H2 gas mass to be between 1 and 20 M⊙ within 300 pc across our sample, where both thermal and nonthermal excitation are involved. Finally, spatial flux maps reveal varied emission structures across all observed gas phases, ranging from radial symmetry around the nucleus to elongated plumes. Kinematic maps also show each galaxy has unique velocity structures despite all being isolated, affirming the diversity of the rotation curves problem, a long-standing tension between simulations and observations. These results showcase the unique and varied nuclear environments that can be found in dwarf galaxies hosting AGN.