Chetna Duggal

University of Manitoba

Chetna is a Ph.D. student at the University of Manitoba working with Drs. Chris O’Dea

and Stefi Baum. Her research focusses on energy feedback from Active Galactic Nuclei (i.e., accreting supermassive blackholes found in the centers of some massive galaxies) and its impact on the host galaxy’s evolution. A part of her doctoral thesis is dedicated to employing high-resolution Hubble Space Telescope (HST) observations to look for evidence of host-AGN feedback in infant-stage radio galaxies that host young, kiloparsec-scale radio sources, known as Compact Steep Spectrum (CSS) galaxies. The AGN jets in this CSS phase of radio galaxy growth lie entirely within the host galaxy extent. Hence, such radio sources are very likely to interact vigorously with the surrounding gas, driving shocks through the galactic ISM, resulting in the triggering of star formation in the host galaxy. This jet-induced star formation is expected to be a key signature of radio-mode feedback on galaxy scales.

Ultraviolet continuum emission offers direct diagnostic for the hot, massive stellar the population that traces new star formation. So, in a recently published study (http://doi.org/10.1002/asna.20210054), she used HST/UV imaging to map star forming regions in a sample of compact radio galaxies and morphologically separate the generic star formation from that associated with the galaxy-scale jet activity. Extended UV emission regions were observed in six of the seven CSS sources showing close spatial alignment with the radio-jet orientation, which suggests a dynamic feedback relationship between jet activity and the host galaxy ISM. If other mechanisms possibly contributing to the observed UV emission are ruled out, this could be evidence in support of jet-triggered star formation in the CSS phase of radio galaxy evolution and in turn of the positive host-AGN feedback paradigm.

A visual comparison of the UV and optical band images of the CSS host galaxies shows the distribution of the younger stellar populations, as evident from UV continuum emission, relative to the general galaxy morphology. (Top panel) HST/WFC3 optical continuum images of our sample of six CSS radio galaxies with overlaid radio contours tracing the jet structure. (Bottom panel) HST UV continuum images of corresponding sources overlaid with contours from VLA radio data, drawing a comparison of the locations of the UV-emitting, likely star forming regions with respect to the general galaxy morphologies in the optical. Note the clumpy, extended UV emission is co-spatial and aligned with the radio-jet orientation.