Kelly E. Lockhart

Welcome! I'm a sixth-year graduate student at the Institute for Astronomy.
My research focuses on galaxy centers: both how stars form there and their connection to galaxy evolution.


My research focuses on the centers of galaxies outside of the Milky Way. I'm particularly interested in how the center of a galaxy can affect its host galaxy's evolution, and how stars continue to form in such extreme environments.

My current research focuses on the nuclear stellar cluster (NSC) of M31, which has an unusual morphology: two redder peaks each less than 10 pc from the black hole, and one very blue cluster within half a pc of the black hole. Observations have shown that the red peaks are the periapse and apoapse sides of an eccentric disk of old stars orbiting the black hole, while the blue cluster is a younger (<200 Myr) population. There's very little molecular gas within the inner 300 pc of the galaxy, so how did this cluster form? I'm using adaptive optics corrected, near IR integral field observations from Keck/OSIRIS to answer this question - stay tuned!

HST/ACS image of the M31 nucleus and WIYN/KPNO of the larger M31 disk. In the inset showing the nuclear region (measuring 3"=11.2 pc on a side), the older nuclear disk is seen as the eccentric reddish disk, while the YNC is the compact blue source.
Source: NASA, ESA, and T. Lauer (NOAO)

In my previous work, we showed that activity in the center of the galaxy is ejecting large amounts of X-ray emitting gas on multi-kpc scales and could help transform this system into its final state. In this study, we focused on the center of Arp 220, the closest ultraluminous IR-bright galaxy (ULIRG) to our own galaxy. This galaxy has recently undergone a major merger; in fact, the two black holes have not yet coalesced and are separated by only a few hundred pc. In our new HST/WFC3 narrow band imaging, we found a 600 pc ionized gas superbubble (seen in Hα + [NII]), which is aligned with the multi-kpc hot gas outflow (seen in X-rays) from this system. Considering the amount of ionized gas in this structure and using energetics arguments, this bubble must be formed by a low-luminosity AGN turning on in the western black hole, or by the high levels of star formation within 100 pc of the black hole.

Figure from Lockhart et al. 2015. In both, our new HST/WFC3 imaging of Arp 220 is shown in green (Hα ionized gas) and blue (F621M continuum). The red filter is the NICMOS F160W image, showing cooler stars and hot gas. The white vector shows the major axis of the large-scale soft X-ray outflow and massive super star clusters are shown with white crosses (both from the literature). The left panel shows the main disk of the system, while the right panel shows the close-up view of the bubble. In both, the correspondence between the western nucleus, bubble, and large-scale outflow is visible.

I'm also a member of the Keck/OSIRIS data reduction pipeline working group. Work is ongoing to improve the pipeline; our latest release can be found here.


My CV is here (updated 1 Oct 2016).

Publications and Talks



First author

  • "HST/WFC3 Observations of an Off-Nuclear Superbubble in Arp 220"
    Lockhart, K. E., Kewley, L. J., Lu, J. R., et al. 2015, ApJ, 810, 149

First author, in prep

  • "A Precessing Disk in the Nucleus of M31 as the Feeding Mechanism for a Central Starburst"
    Lockhart, K. E., Lu, J. R., et al.


  • "Testing Theories of in situ Star Formation in M31," Keck Science Meeting, September 2016
  • "Testing Theories of in situ Star Formation in M31," UT Austin department seminar, September 2016
  • "Small Scale Origins of Large Scale Galactic Feedback," UC Irvine department seminar, February 2015
  • "Small Scale Origins of Large Scale Galactic Feedback," UCLA, February 2015


Kelly E. Lockhart
Institute for Astronomy
University of Hawaii, Manoa
2680 Woodlawn Drive
Honolulu, HI 96814