Poster Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

Colour bimodality of galaxies at high redshift (#251)

Themiya Nanayakkara 1
  1. CAS, Hawthorn, VIC, Australia

One of the main methods that is being used to describe galaxies is their colour morphology. Many studies in the past has focused on low redshift galaxies and has found many interesting results on the dependence of colour of galaxies on environment and mass1 2 .

With the introduction of many large scale surveys, at present there are many studies which try to identify properties of galaxies at high redshift6 3 . The study of them is important to try to understand the formation and evolution of individual galaxies and galaxy clusters.

Therefore it is important to try to investigate comparisons between field and cluster galaxies at high redshift and compare them with results from low redshift studies. One of the main impediments for such studies is the lack of galaxy clusters identified at higher redshifts. In 2011 the first results from Z-FOURGE survey revealed a candidate cluster in the COSMOS field around a redshift of two, which possibly is the highest redshift cluster identified so far5 .

While better resolution redshift data is required to properly establish whether it is a cluster or a group of galaxy overdensities, one of the main aims in my current study is to try identify the colour distribution of the galaxies at the higher redshifts. I am planning to study how the colour bimodality depends on galaxy environment (which itself is defined in many ways4 ) and/or mass at high redshift and compare results with the SDSS studies done by Baldry et al. using galaxies around a redshift of two and observed K magnitude cutoff at 24.8. The ultimate goal would be to try to compare results with semi analytic models by Croton and Peng et al. to establish constrains on galaxy evolution for future studies.

  1. I. K. Baldry, M. L. Balogh, R. G. Bower, K. Glazebrook, R. C. Nichol, S. P. Bamford, and T. Budavari. Galaxy bimodality versus stellar mass and environment. , 373:469{483, December 2006.
  2. I. K. Baldry, K. Glazebrook, J. Brinkmann, Z. Ivezic, R. H. Lupton, R. C. Nichol, and A. S. Szalay. Quantifying the Bimodal Color-Magnitude Distribution of Galaxies. , 600:681{694, January 2004.
  3. K. Kovac et al. The Density Field of the 10k zCOSMOS Galaxies. , 708:505{533, January 2010.
  4. S. I. Muldrew, D. J. Croton, R. A. Skibba, F. R. Pearce, H. B. Ann, I. K. Baldry, S. Brough, Y.-Y. Choi, C. J. Conselice, N. B. Cowan, A. Gallazzi, M. E. Gray, R. Grutzbauch, I.-H. Li, C. Park, S. V. Pilipenko, B. J. Podgorzec, A. S. G. Robotham, D. J. Wilman, X. Yang, Y. Zhang, and S. Zibetti. Measures of galaxy environment - I. What is 'environment'? , 419:2670{2682, January 2012.
  5. L. R. Spitler, I. Labbe, K. Glazebrook, S. E. Persson, A. Monson, C. Papovich, K.-V. H. Tran, G. B. Poole, R. Quadri, P. van Dokkum, D. D. Kelson, G. G. Kacprzak, P. J. McCarthy, D. Murphy, C. M. S. Straatman, and V. Tilvi. First Results from Z -FOURGE: Discovery of a Candidate Cluster at z = 2.2 in COSMOS. , 748:L21, April 2012.
  6. K. E. Whitaker, I. Labbe, P. G. van Dokkum, G. Brammer, M. Kriek, D. Marchesini, R. F. Quadri, M. Franx, A. Muzzin, R. J. Williams, R. Bezanson, G. D. Illingworth, K.-S. Lee, B. Lundgren, E. J. Nelson, G. Rudnick, T. Tal, and D. A. Wake. The NEWFIRM Mediumband Survey: Photometric Catalogs, Redshifts, and the Bimodal Color Distribution of Galaxies out to z ~ 3. , 735:86, July 2011. 2