BAL Quasar with Post-Starburst Features

 

BAL quasars are named after the presence of broad absorption lines on the blue side of the normal quasar emission lines. These arise from material that is in an outflow state, presumably launched by the central accreting supermassive black hole. These absorption lines often span thousands of kilometers per second. We find one such object in the DES (Dark Energy Survey) Supernova fields that also has a significant post-starburst population in its spectrum, the first of its kind known. The host galaxy has strong, high order Balmer features which let us model how long ago star formation was quenched in this system. If we assume that the star formation quenching episode is directly related to the onset of quasar activity, a strong assumption, then this actually gives us an approximate age of the quasar of about 40 million years. This is comparable to the total expected lifetimes of quasars of about 10-100 million years. This is especially interesting because it is argued many of these BAL quasars with iron and other low-ionization broad absorption lines are young quasars with strong winds that are blowing out central material to shut off the star formation. We suggest that this implies this object may have its observed BAL features due to a blast wave from the quasar that has impacted a dense cloud along our line of sight instead, as has been proposed in alternative models by other works.

"Discovery of a z=0.65 Post-Starburst BAL Quasar in the DES Supernova Fields"
Mudd, D.M. and the DES Collaboration, MNRAS Submitted
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M33 UV Catalog

 

The hottest stars (>10,000 K), and, by extension, typically the most massive ones, are those that will be prevalent in ultraviolet wavelengths. Working with Dr. Krzysztof Stanek and using GALEX combined with ground-based data, I am constructing a UV to optical catalog of the nearby galaxy M33, the next-largest member of the Local Group after Andromeda and our own Milky Way.

"GALEX Catalog of UV Point Sources in M33"
Mudd, D.M. and Stanek, K.Z. 2014, MNRAS, 450, 3811
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Star Formation and AGN Activity in Merging Galaxies

 

Working with Dr. Smita Mathur, I investigated the prevalence of dual active galactic nuclei (AGN) in merging systems using x-rays. Hierarchical models have suggested that galaxy mergers are ideal environments for turning on AGN. Tidal torques induced by the merger process are predicted to send gas to the centers of the galaxies, which can then be used to fuel enhanced star formation and/or black hole growth. These systems are often very dusty and heavily obscured in optical wavelengths, so probing them with x-rays is one of the few ways available to try and get a full look at the physics going on behind the dusty curtain. Using XMM-Newton, we look at 3 nearby merging systems. In one we find two separate nuclear point sources for the galaxies, but the cores of the individual galaxies in the other two systems are unresolved. Modeling the spectra, we find that the x-rays are likely related to the elevated star formation rather than AGN, but we cannot conclusively rule them out.

"XMM-Newton Observations of Three Interacting Luminous Infrared Galaxies"
Mudd, D.M. et al. 2014, ApJ, 787, 40
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The "Changing-Look" AGN in NGC 2617

 

The All-Sky Automated Survey for SuperNovae (ASAS-SN) found a brightening in the core region of NGC 2617, a known Seyfert galaxy, which was then followed by a multi-month photometric and spectroscopic monitoring campaign in multiple wavelengths. The galaxy showed many interesting phenomena associated with this increased flux, including switching from a Seyfert 1.8 to a Seyfert 1 due to the appearance of optical broad emission lines. This is one of only a few known instances of an AGN's broad lines appearing. Features in the outburst are shown to start in the x-rays with (presumably) the disk lagging behind by several days, with slightly longer lags for the UV and the longest ones for the NIR.

"The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617"
Shappee, B.J. et al 2014, ApJ, 788, 48
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