Dr. Marc S. Seigar

Astrophysics Research Group

University of Arkansas at Little Rock


Image credits: NASA/JPL-Caltech/Harvard-Smithsonian CfA/NOAO

Research


Structure, Morphology, and dynamics of nearby galaxies:
Since completing my PhD, I have been interested in the overall structure, morphology and dynamics of nearby galaxies, especially disk galaxies. I am involved in the Arkansas Galaxy Evolution Survey (AGES), part of which is to conduct a census of supermassive black holes in the Universe.

Selected Publications:

  • "The Carnegie-Irvine Galaxy Survey. I. Overview and Atlas of Optical Images." Ho, Li, Barth, Seigar, & Peng. (2011, ApJS).
  • "Galaxy Rotation Curves in the Context of LCDM Cosmology." Seigar & Berrier. (2011, Advances in Cosmology).
  • The Dark Matter Halo Density Profile, Spiral Arm Morphology, and Supermassive Black Hole Mass of M33." Seigar. (2011, ISRN).
  • "A revised Mass Model for the Andromeda Galaxy." Seigar, Barth, & Bullock. (2008, MNRAS).
  • "Discovery of a relationship between spiral arm morphology and supermassive black hole mass in disk galaxies." Seigar, Kennefick, Kennefick, & Lacy. (2008, ApJL).
  • "Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. I. Method outline." Seigar, Bullock, Barth, & Ho. (2006, ApJ).
  • "Dust-penetrated arm classes: insights from rising and falling rotation curves." Seigar, Block, Puerari, Chorney, & James. (2005, MNRAS).


Direct Dark Matter Searches:
I am involved in the DarkSide project. DarkSide (Depleted Argon cryogenic Scintillation and Ionization Detection) is an experimental collaboration for the detection of Weakly Interacting Massive Particles (WIMPs), a proposed form of dark matter. Its scientific program is planned in phases with increasing sensitivity. The first step is Darkside-50, a dual-phase, 50 kg depleted argon time projection chamber (TPC). WIMPs would be detected when they scatter off an argon nucleus in the bulk liquid argon target. The nucleus recoils leaving a short track of ionized argon. Molecular processes of electronic recombination produce a flash of scintillation light detected by arrays of photomultiplier tubes (PMTs). By applying an electric field, a fraction of the electrons are drifted to the anode grid, multiplied in the gas phase above the liquid argon and detected as a second signal. This dual readout allows us to distinguish nuclear recoils from other background events. Darkside-50 will be deployed at the Gran Sasso underground laboratories in Italy. The second phase of DarkSide is within a larger project called MAX (Multi-ton Argon and Xenon detectors), which also includes the XENON collaboration. The plan is to run dual-phase ton-sized depleted argon and xenon detectors side by side, to validate discovery claims with different targets.


Star Formation in Galaxies:
I am interested in the mechanisms responsible for the formation of stars in quiescent spiral galaxies. In the widely accepted theory of spiral density waves, triggering of star formation by shocks in spiral arms would lead to the formation of HII regions downstream of density waves. This was one of the goals of theH-alpha Galaxy Survey, in which I am a co-investigator.

Selected Publications:

  • "The connection between shear and star formation in spiral galaxies." Seigar. (2005, MNRAS).
  • "The H-alpha galaxy survey. I. The galaxy sample, H-alpha narrow-band observations and star formation parameters for 334 galaxies." James et al. (Seigar 13th author). (2004, A & A).
  • "A test of arm-induced star formation in spiral galaxies from near-infrared and H-alpha imaging." Seigar & James. (2002, MNRAS).


Clusters of Galaxies:
cD galaxies have been known to have outer stellar envelopes for many decades. This is now believed to be a manifestation of intracluster light (ICL) that Zwicky first detected in the 1950s. This intracluster light is believed to be material that is stripped tidally from cluster member galaxies as they interact and/or merge with each other. Another indication of this activity in clusters is the multiple nuclei often seen in the brightest cluster galaxies (BCGs). The Large Synoptic Survey Telescope will help us to further determine the nature of ICL.

Selected Publications:

  • "Intracluster light and the extended stellar envelopes of cD galaxies: An analytical description." Seigar, Graham, & Jerjen. (2007, MNRAS).
  • "A triple nucleus in the brightest cluster galaxy in Abell 193." Seigar, Lynam, & Chorney. (2003, MNRAS).