Accretion on the spot!
Galaxies grow in mass and size over cosmic time, both as a result of mergers, and via accretion of gas from the circumgalactic medium. As the inflow dilutes the metals in the gas, the metallicity distribution becomes a powerful way to search for gas accretion. Advised by Tim Heckman, Jorge Barrera-Ballesteros and Kate Rowlands, Hwang et al. (2019) search for these low-metallicity regions in nearby galaxies. These regions (blue and purple spaxels in the panels) are present in both interacting and non-interacting galaxies. These low-metallicity regions may be signposts to galaxies caught in the act of growing via accretion.
Winds as the origin of radio emission in radio-quiet quasars
The origin of radio emission in radio-quiet quasars is still not well understood. In the scenario of quasar wind, the synchrotron emission in radio is a by-product of radiatively driven winds. Advised by Nadia L. Zakamska, Hwang et al. (2018) investigated this by studying the population of extremely red quasars, who are among the most powerful quasars in the Universe. They (orange and red symbols in the figure) closely follow the correlation between [OIII] velocity width (wind indicator) and radio luminosity, strongly supporting that wind as a contributor to radio emission in radio-quiet quasars.
