Research

Black holes in dwarf galaxies can provide important constraints on the formation and growth of supermassive black holes seen in almost all massive galaxies. However, we still do not know how many dwarf galaxies host massive black holes or the properties of the dwarf galaxy black hole population.

My work focuses on identifying black holes in nearby dwarf galaxies, and understanding their effect on their host galaxy. As PI of an accepted Gemini observing program, I led follow-up on the Reines et al. (2020) wandering black hole sample, and found a surprisingly strong detection of the [Fe X] coronal line in one of the observed galaxies.

Based on that work, I led the first systematic search for coronal-line emission in dwarf galaxies with SDSS single-fiber spectroscopy. I found a sample of 81 black hole candidates in very low-mass, blue galaxies easily missed by other detection methods. This study demonstrates the power of this selection method at constraining the elusive low-mass end of the black hole population in dwarf galaxies.

Related Papers: Molina et al. (2021b), Molina et al. (2021a), Kimbro et al. (2021), Reines et al. (2020)

50% of all nearby galaxies are low ionization nuclear emission regions (LINERs) and harbor weakly-accreting active black holes called active galactic nuclei (AGN). However, traditional AGN photoionization models cannot explain the emission we see, implying that some other power source is significantly contributing to the overall energy budget.

I used high-resolution Hubble Space Telescope (HST) long-slit spectroscopy to study the central regions of three LINERs. I found that AGN photoionization dominates the energy budget in the very center, or nuclei, of these galaxies, while AGN-related shocked emission dominates at larger distances away from the black hole (20 pc and beyond). This means that AGN feedback plays an important role in these three LINERs with weakly-accreting black holes.

My work led to an accepted HST observing program (Cycle 29, 34 orbits) to study a diverse and representative sample of 15 nearby LINERs with weakly-accreting black holes. Our sample covers a wide range of host galaxy environments, including a variety of radio properties (from compact to large, double-lobed emission) and varying stellar contributions, including several objects where the stars actually contribute more ionizing photons than the AGN. This work will provide strong constraints on the relative importance of feedback for low-luminosity AGNs, and their interactions with their host galaxies.

Related Papers: Molina et al. (2018)

Star formation and its quenching is crucial to understanding galaxy evolution, but is not well-understood. In order to fully explore how star formation is quenched in galaxies, we need spatially resolved star formation histories across the faces of galaxies, as well as accurately accounting for the effects of dust.

In order to study these questions, I created a catalog of 150 galaxies with both MaNGA optical integrated field unit (IFU) spectroscopy and Swift near ultra-violet (NUV) images. We created spatially-matched maps of the Swift NUV images, SDSS optical images and MaNGA IFU emission line, equivalent width and spectral index maps of these galaxies to create the Swift+MaNGA (SwiM) catalog. The SwiM catalog allows for unprecedented, simultaneous NUV-optical studies of spatially-resolved star formation in nearby galaxies at the same angular resolution. Using this catalog, I explored spatially resolved dust attenuation in nearby galaxies. I found that stellar attenuation varies significantly within a single galaxy, while the reddening of emission lines is generally similar to the global value.

The SwiM catalog is the basis of a selected NASA ADAP program to study dust properties, star formation quenching and star formation histories in the local Universe. I am also the PI of a Swift observing program to expand the catalog to be similar to the galaxy distribution seen in MaNGA. The new work from both programs will allow for statistical studies of the evolution of star formation and dust properties of galaxies in the local universe.

Related Papers and Catalogs: Molina et al. (2020a), Molina et al. (2020b), SwiM VAC