Galaxy formation and evolution through the cosmic time, environmental dependances of galaxy properties, galaxy mergers.

I am working with Prof. Simon Lilly on problems related to galaxies from zCOSMOS & COSMOS projects.

Cosmic Evolution Survey (COSMOS) - is an astronomical survey designed to probe the formation and evolution of galaxies as a function of cosmic time (redshift) and large scale structure environment. The survey covers a 2-square-degree equatorial field with imaging by most of the major space-based telescopes (Hubble, Spitzer, GALEX, XMM, Chandra) and a number of large ground-based telescopes (Subaru, VLA, ESO-VLT, UKIRT, NOAO, CFHT, and others). Over 2 million galaxies are detected in the survey, spanning 75% of the age of the universe. COSMOS involves over 100 scientists in a dozen countries.

zCOSMOS  is a project that adds the 3rd dimension to the galaxies in the COSMOS field. It is a largest spectroscopic survey on the ESO VLT, with approved 600 hours of observations. The zCOSMOS-bright part of the survey will ultimately obtain over 20,000 spectra selected to have I(AB) < 22.5. With this flux limit, the redshift range of the majority of the observed galaxies will be 0< z< 1.4. The z zCOSMOS-deep programme aims for higher redshift range, 1.4< z< 3 using various colour-selection criteria. Currently we are operating on the first ~10,000 spectra from the zCOSMOS-bright, which we refer to as the ``10k sample''.

We used a multicolour data from SDSS to reproduce as accurately as possible the appearance that they would have on COSMOS ACS images if they had been observed at redshifts z ~ 0.7 and z ~ 1.2. These simulations include surface brightness dimming, the effects of band-pass shifting, the changing spatial resolution, and the increased noise. By adding the SDSS galaxies to random locations in the COSMOS images, we also simulate the effects of chance superpositions of high redshift galaxies with unrelated foreground or background objects. This representative sample of 1813 galaxies proved to be well suited and useful for a number of studies, where evolution of various galaxy properties (like sizes, morphologies, surface brightness) as a function of redshift had to be precisely determined.

We use the simulated images in a direct comparison with a large sample of real COSMOS galaxies at zphot ~ 0.7 and 1.2, to assess the redshift evolution of the fraction of visually-classified galaxy mergers from the present epoch up to z ~ 1. Our approach in this work was to try to ensure that possible subjectivity in classification is at least independent of redshift. This was achieved both through use of the simulated images to remove the redshift dependent observational biases and through a rigorous “blind” methodology to eliminate any personal biases on the part of the classifier. In this work we also estimated how large can be a fraction of mergers (mis-)classified due to chance projections with unrelated objects that were already present on the ACS images. Number of those spurious identifications turned out to be ~40% at redshift ~0.7, showing importance of simulations as done here in any determination of merging fractions based on the morphological features. More details can be found in ApJ COSMOS Special Issue:  "Simulating the COSMOS: The fraction of merging galaxies at high redshift." P. Kampczyk, S. J. Lilly, C. M. Carollo, C. Scarlata, R. Feldmann, A. Koekemoer, A. Leauthaud, Y. Taniguchi, P. Capak; ApJS 2007, 172, 329.
Full text available here. See also poster in the pdf format.

Current zCOSMOS 10k sample enabled us to study the close kinematic pair of galaxies, which are presumably progenitors of the future galaxy mergers. Using various density field estimators derived for the 10k sample we estimate the environmental impact on the close kinematic pair fractions as well as on the morphological mix of the galaxies in pairs. We investigate changes of various properties, including SFR & SSFR in those pre-merging systems. Coming soon…

• More about the current research projects in our group
• More about our recent results

• P. Kampczyk, S. J. Lilly, C. M. Carollo, et al.
  “Simulating the Cosmos: The Fraction of Merging Galaxies at High Redshift”,
  Astrophys. J. Supp. 172, 329 (2007)
• S. J. Lilly, O. Le Fevre, A. Renzini, ..., P. Kampczyk, et al.
  “zCOSMOS: A Large VLT/VIMOS Redshift Survey Covering 0 < z < 3 in the COSMOS Field”,
  Astrophys. J. Supp. 172, 70 (2007)
• C. Scarlata, C. M. Carollo, S. J. Lilly, ..., P. Kampczyk, et al.
  “COSMOS Morphological Classification with the Zurich Estimator of Structural Types (ZEST) and the Evolution Since z = 1 of the Luminosity Function of Early, Disk, and Irregular Galaxies”,
  Astrophys. J. Supp. 172, 406 (2007)
• M. T. Sargent, C. M. Carollo, S. J. Lilly, ..., P. Kampczyk, et al.
  “The Evolution of the Number Density of Large Disk Galaxies in COSMOS”
   Astrophys. J. Supp. 172, 434 (2007)

• C. Scarlata, C. M. Carollo, S. J. Lilly, ..., P. Kampczyk, et al.
  “The Redshift Evolution of Early-Type Galaxies in COSMOS: Do Massive Early-Type Galaxies Form by Dry Mergers?“,
  Astrophys. J. Supp. 172, 494 (2007)
  
• K. I. Caputi, S. J. Lilly, H. Aussel, ..., P. Kampczyk, et al.
  “The Optical Spectra of 24 μm Galaxies in the COSMOS Field. I. Spitzer MIPS Bright Sources in the zCOSMOS-Bright 10k Catalog”
   Astrophys. J. 680, 939 (2008)

• R. Mandelbaum, U. Seljak, C.M. Hirata, ..., P. Kampczyk, et al.
  “Precision photometric redshift calibration for galaxy-galaxy weak lensing”
    Mon. Not. Roy. Astron. Soc. 386, 781 (2008)

• M. Mignoli, G. Zamorani, A. Cimati, ..., P. Kampczyk, et al.
  “The zCOSMOS redshift survey: the three-dimensional classification cube and bimodality in galaxy physical properties”
   Astronomy & Astrophysics 493, 39 (2009)

• R. Gili, G. Zamorani, T. Miyaji, ..., P. Kampczyk, et al.
  “The spatial clustering of X-ray selected AGN in the XMM-COSMOS field”
   Astronomy & Astrophysics 494, 33 (2009)

• L. A. M. Tasca, J.-P. Kneib, A. Iovino, ..., P. Kampczyk, et al.
  “The zCOSMOS redshift survey: the role of environment and stellar mass in shaping the rise of the morphology-density relation from z ~ 1”
   Astronomy & Astrophysics 503, 379 (2009)

• B. Meneux, L. Guzzo, S. de La Torre, ..., P. Kampczyk, et al.
  “The zCOSMOS survey. The dependence of clustering on luminosity and stellar mass at z=0.2-1”
   Astronomy & Astrophysics 505, 463 (2009)

• O. Ilbert, P. Capak, M. Salvato, ..., P. Kampczyk, et al.
  “Cosmos Photometric Redshifts with 30-Bands for 2-deg2”
   Astrophys. J. 690, 1236 (2009)

• K. I. Caputi, K. Kovac, M. Bolzonella, ..., P. Kampczyk, et al.
  “The Close Environment of 24 μm Galaxies at 0.6 < z < 1.0 in the Cosmos Field”
   Astrophys. J. 680, 939 (2009)

• C. Maier, S. J. Lilly, G. Zamorani, ..., P. Kampczyk, et al.
  “The Dependence of Star Formation Activity on Stellar Mass Surface Density and Sersic
  Index in zCOSMOS Galaxies at 0.5 < z < 0.9 Compared with SDSS Galaxies at 0.04 < z < 0.08”
   Astrophys. J. 694, 1099 (2009)

• J. D. Silverman, K. Kovac, C. Knobel, ..., P. Kampczyk, et al.
  “The Environments of Active Galactic Nuclei within the zCOSMOS Density Field”
   Astrophys. J. 695, 171 (2009)

• J. D. Silverman, F. Lamareille, C. Maier, ..., P. Kampczyk, et al.
  “Ongoing and Co-Evolving Star Formation in zCOSMOS Galaxies Hosting Active Galactic Nuclei”
   Astrophys. J. 696, 396 (2009)

• C. Knobel, S. J. Lilly, A. Iovino, ..., P. Kampczyk, et al.
  “An Optical Group Catalog to z = 1 from the zCOSMOS 10 k Sample”
   Astrophys. J. 697, 1842 (2009)

• Simon J. Lilly, Vincent Le Brun, Christian Maier, ..., Pawel Kampczyk, et al.
  “The zCOSMOS 10k-Bright Spectroscopic Sample”,
  Astrophys. J. Supp. 184, 218 (2009)