Project:	Quasar or Starburst? The Shimmering Facets of Galaxies
Disciplines:	Astrophysics, Astronomy
Mentor:	George Helou, Prof, (PMA), ghelou@caltech.edu, Phone: 6263958585
Mentor URL:	http://5muses.ipac.caltech.edu/index.html/index.html  (opens in new window)
AO Contact:	George Helou, ghelou@caltech.edu
Background:	Galaxy evolution is the critical thread that leads from the primordial fireball to today's complex universe and its huge range of conditions from neutron stars to life-supporting planets. Galaxy evolution is driven largely by star formation and black hole accretion, entwined processes that run steadily then burst at times to excessive levels labeled as starbursts or quasars. Today's galaxies encode in their stellar content and their nuclear black holes the history and connections of these processes; their luminosity still derives from a combination of these processes. A few reliable tests to discern the source of observed luminosity have been established, but these are not perfectly consistent because of the rich physics that enters the interpretation of each test. Better understanding of galaxy evolution starts with a clearer understanding of how these tests relate empirically, what that implies about their physical meaning, and how to translate these implications into better tests at different redshifts to reconstruct cosmic history.
Description:	The student will participate in the analysis of data from space-based (Spitzer, WISE/NEOWISE) and ground-based facilities (ZTF) for a sample of galaxies carefully selected to represent infrared emitting galaxies within the last few billion years. These data include infrared spectroscopic indices that signal the relative importance of star formation or black hole accretion in the emitted luminosity; they also include time-domain data where variability points to the dominant role of accretion as a luminosity source. The analysis will focus on comparing the various indices and tests to develop a description of the current activity and configuration of each galaxy. The resulting descriptions will then form the basis of a statistical picture of this sample and implications for recent evolution of galaxies.
References:	Extended Schmidt Law: Role of Existing Stars in Current Star Formation (Shi, Yong; Helou, George; Yan, Lin; Armus, Lee; Wu, Yanling; Papovich, Casey; Stierwalt, Sabrina) [ https://ui.adsabs.harvard.edu/abs/2011ApJ...733...87S/abstract ] The Mid-infrared Luminosity Function at z < 0.3 from 5MUSES: Understanding the Star Formation/Active Galactic Nucleus Balance from a Spectroscopic View (Wu, Yanling; Shi, Yong; Helou, George; Armus, Lee; Dale, Daniel A.; Papovich, Casey; Rahman, Nurur; Dasyra, Kalliopi; Stierwalt, Sabrina) [ https://ui.adsabs.harvard.edu/abs/2011ApJ...734...40W/abstract ] Infrared Luminosities and Aromatic Features in the 24 µm Flux Limited Sample of 5MUSES (Wu, Yanling; Helou, George; Armus, Lee; Cormier, Diane; Shi, Yong; Dale, Daniel; Dasyra, Kalliopi; Smith, J. D.; Papovich, Casey; Draine, Bruce; Rahman, Nurur; Stierwalt, Sabrina; Fadda, Dario; Lagache, G.; Wright, Edward L.) [ https://ui.adsabs.harvard.edu/abs/2010ApJ...723..895W/abstract ]
Student Requirements:	Interest in physics or astrophysics and knowledge of basic concepts is preferred. Experience with Python programming and basic statistical concepts either in a class or independent projects is preferred.
Programs:	This AO can be done under the following programs:   Program    Available To        SURF    both Caltech and non-Caltech students  Click on a program name for program info and application requirements.