Valsamo (Vallia) Antoniou

Faculty
Ph.D. 2008 University of Crete
Affiliate Assistant Professor
Astronomy

A419 Zaffarano Hall
vallia [at] iastate [dot] edu
515-294-9907


 

Short Biography

I received my Ph.D. in Astrophysics from the University of Crete, Greece on May 2008. A large part of my research has been performed at the Harvard-Smithsonian Center for Astrophysics, as a visiting graduate student (2004-2007) and as a visiting scientist (2008-2009). After that, I joined Iowa State University, where I worked as a postdoctoral research associate for 6 months. Currently (since June 2010), I am employed as an affiliated assistant professor. 
 
 
Research Interests
 
My research has been focused on understanding the underlying mechanisms of accreting binary formation and evolution with the aim to address the following questions:
    ✧ What are the properties of the overall accreting X-ray binary (XRB) population, and the relative contribution of the various components? 
    ✧ What is their formation rate?
    ✧ What is the effect of metallicity and post-starburst age on their formation and evolution?
    ✧ How does the X-ray luminosity function (XLF) depend on these parameters? 
My aim is to establish a well-defined framework of XRB evolution that will enable the use of extragalactic XRBs as a star-formation diagnostic. The Magellanic Clouds, our two nearest star-forming galaxies, are used as controlled laboratories. For their study I use data from space observatories like the Chandra and XMM-Newton X-ray telescopes and from optical ground-based facilities in Chile (e.g., the 6.5m Magellan-Baade telescope at Las Campanas Observatory, the 4m V. M. Blanco telescope at CTIO, and the 2.2m MPG/ESO telescope at La Silla Observatory).
 

Another aspect of my work is related to one of the most common problems in astrophysics, i.e. the classification of astronomical sources based on their colors and magnitudes. Currently, I am strongly involved on the classification of ~6M infrared point sources in the Large Magellanic Cloud detected with the Spitzer Space Telescope.

     The question is obvious: Can we reliably classify all these sources? For this reason, we use a statistical approach based on the weighted k-Nearest Neighbors (k-NN) method (following Marengo & Sanchez 2009, AJ, 138, 63), which has been successfully used as an efficient “black box” predictor for problems of pattern recognition and unsupervised machine learning. A metric is defined in a multi-dimensional color-magnitude space, based only on the photometric properties of template sources and the photometric uncertainties of both templates and data, as a function of the k-NN number and a threshold distance Dth.

 
 
Selected Publications 

⎔ Antoniou, V. & Zezas, A. 2012, Star Formation History and X-ray Binary Populations: The Case of the Large Magellanic Cloud, ApJ subm.

⎔ Woods, P. M., Oliveira, J. M., Kemper, F., and 54 coauthors 2011, The SAGE-Spec Spitzer Legacy program: The life-cycle of dust and gas in the Large Magellanic Cloud. Point Source classification, MNRAS, 411, 1597

⎔ Antoniou, V., Zezas, A., Hatzidimitriou, D. & Kalogera, V. 2010, Star Formation History and X-ray Binary Populations: The Case of the Small Magellanic Cloud, ApJL, 716, 140

⎔ Laycock, S., Zezas, A., Hong, J., Drake, J. J., Antoniou, V. 2010, Exploring the Small Magellanic Cloud to the Faintest X-ray Fluxes: Source Catalog, Timing, and Spectral Analysis, ApJ, 716, 1217

⎔ Kemper, F., Woods, P. M., Antoniou, V., and 53 coauthors 2010, The SAGE-Spec Spitzer Legacy Program: The Life Cycle of Dust and Gas in the Large Magellanic Cloud, PASP, 122, 683

⎔ Antoniou, V., Hatzidimitriou, D., Zezas, A., & Reig, P. 2009, Optical spectroscopy of 20 Be/X-ray Binaries in the Small Magellanic Cloud, ApJ, 707, 1080

⎔ Antoniou, V., Zezas, A., Hatzidimitriou, D. & McDowell, J. 2009, The Chandra survey of the SMC ``Bar": II. Optical counterparts of X-ray sources, ApJ, 697, 1695