Choong's Home Page

UIUC Department of Astronomy

cngeow_youknowthesymbol_astro.uiuc.edu



Personal Information

1. Last name: Ngeow; First name: Chow Choong
2. Home country: Malaysia.
3. Undergrad college: Ohio State University, Columbus. B.S. in Astronomy (1999).
4. Graduate college: University of Massachusetts, Amherst, Ph.D. in Astronomy (2005).
5. First postdoc position in University of Illinois (Urbana-Champaign).

Curriculum Vitae

My CV (will be updated periodically).

Research

Current main research areas:

A. Cepheid Variables and Distance Scale
I am interested in Distance Scale & Cosmology, in particular the use of Cepheid variables in the distance scale problems. I have been working on these problems which include the refinement of Cepheid light-curves fitting methods, distance scale comparison to NGC 1637, and detailed investigation regarding the non-linearity and non-universality of the Cepheid period-luminosity relation. Most of these works were done during my PhD Thesis years (with my Thesis Advisor: Dr. Shashi Kanbur, see the research page in my UMASS homepage for further details).

B. Data Management for Dark Energy Survey (DES)
As for the first post-doctoral position, I am part of the DES Data Management team under the supervision of Dr. Joe Mohr. The tasks involve in this project include the development and testing of the automatic reduction pipelines for the up-coming DES project. See UIUC DES main site for further details.

C. Blanco Cosmological Survey (BCS)
I am also part of the BCS collaboration. As a result, I have an observing opportunity with the CTIO Blanco 4m telescope.

D. Galaxy Angular Power Spectrum
I am also interested in the calculation of galaxy's angular power spectrum. I am learning and developing the codes at the moment as well.

Publications

    Cepheids: Light Curves and Distance Scale
  1. Reconstructing Cepheid Light Curves with Fourier Techniques I: Fourier Expansion and Interrelations, by Ngeow, C. C., Kanbur, S. M., Nikolaev, S., Tanvir, N. & Hendry, M., 2003, ApJ 586:959.
  2. Reconstructing Cepheid Light Curve with Fourier Expansion and Interrelations, by Ngeow, C. C., Kanbur, S. M., Nikolaev, S., Tanvir, N. & Hendry, M., 2003, in "Focus on Astrophysics Research", Ed. Ross, Nova Science Publisher.
  3. The Cepheid Distance to NGC 1637: A Direct Comparison with the EPM Distance to SN 1999em, by Leonard, D., Kanbur, S., Ngeow, C. C. & Tanvir, N., 2003, ApJ 594:247.
  4. Extra-Galactic Cepheid Distance from Large Magellanic Cloud and Galactic Period-Luminosity Relations, by Kanbur, S. M., Ngeow, C. C., Nikolaev, S., Tanvir, N. & Hendry, M., 2003, A&A 411:361.
    VizieR On-Line Catalogue: VI photometry of extra-galactic Cepheids
  5. Determination of Cepheid Parameters by Light-Curve Template Fitting, by Tanvir, N., Hendry, M., Watkins, A., Kanbur, S., Berdnikov, L. & Ngeow, C. C., 2005, MNRAS 363:749.
  6. Large Magellanic Cloud Distance from Cepheid Variables using Least Squares Solutions, by Ngeow, C. C. & Kanbur, S., 2008, in "Galaxies in the Local Volume", Ed. Koribalski & Jerjen, Springer, pg 317 (arXiv:0708.0445)

    Cepheids: Period-Luminosity Relation

  7. Period-Luminosity Relations for Galactic Cepheid Variables with Independent Distance Measurements, by Ngeow, C. C. & Kanbur, S., 2004, MNRAS 349:1130.
    Erratum: 2004, MNRAS, 351:768
  8. Cepheid Period-Luminosity Relations: Galactic vs. LMC and the Results from t-Test, by Ngeow, C. C. & Kanbur, S., 2005, in "GAIA: The Three Dimensional Universe with GAIA", ESA.
  9. The Physics Behind the Non-Universality of the Cepheid Period-Luminosity Relation, by Kanbur, S. M. & Ngeow, C. C., 2005, in "GAIA: The Three Dimensional Universe with GAIA", ESA.
  10. The Linearity of the Wesenheit Function for the Large Magellanic Cloud Cepheids, by Ngeow, C. C.. & Kanbur, S. M., 2005, MNRAS 360:1033.
  11. Further Empirical Evidence for the Non-Linearity of the Period-Luminosity Relations as seen in the Large Magellanic Cloud Cepheids, by Ngeow, C. C., Kanbur, S. M., Nikolaev, S., Buonaccorsi, J., Cook, K. & Welch, D., 2005, MNRAS 363:831.
  12. Investigating the Break in the Cepheid Period-Luminosity Relation and Its Implications, Ngeow, C. C., 2006, Dissertation Summary in PASP 118:349.
  13. The Hubble Constant from Type Ia Supernovae Calibrated with the Linear and Nonlinear Cepheid Period-Luminosity Relations, by Ngeow, C. C. & Kanbur, S., 2006, ApJL 642:L29.
  14. Nonlinear Period-Luminosity Relation for the Large Magellanic Cloud Cepheids: Myths and Truths, by Ngeow, C. C. & Kanbur, S., 2006, ApJ 650:180.
  15. Investigations of the Non-Linear LMC Cepheid Period-Luminosity Relation with Testimator and Schwarz Information Criterion Methods, by Kanbur, S., Ngeow, C. C., Nanthakumar, A. & and Stevens, R., 2007, PASP 119:512.
  16. Semi-Empirical Cepheid Period-Luminosity Relations in Sloan Magnitudes, by Ngeow, C. C. & Kanbur, S., 2007, ApJ 667:35.
  17. The Detailed Form of the LMC Cepheid PL and PLC Relations, by Koen, C., Kanbur, S. & Ngeow, C., 2007, MNRAS 380:1440
  18. Testing the Non-Linearity of the BVIcJHKs Period-Luminosity Relations for the Large Magellanic Cloud Cepheids, by Ngeow, C., Kanbur, S. & Nanthakumar, A., 2008, A&A, 477:621
  19. ThePeriod-Luminosity Relation for the Large Magellanic Cloud Cepheids Derived from Spitzer Archival Data, by Ngeow, C. & Kanbur, S., 2008, ApJ, 679:76
  20. Period-Luminosity Relations Derived from the OGLE-III Fundamental Mode Cepheids, by Ngeow, C., Kanbur, S, Neilson, H., Nanthakumar, A. & Buonaccorsi, J., 2009, ApJ in-press (arXiv:0811.2000)

    Cepheids: Series of Period Color - Amplitude Color Relations

  21. Period-Color and Amplitude-Color Relations in Classical Cepheid Variables, by Kanbur, S. & Ngeow, C. C. , 2004, MNRAS 350:962.
  22. Period-Color and Amplitude-Color Relations in Classical Cepheid Variables II: the Galactic Cepheid Models, by Kanbur, S., Ngeow, C. C. & Buchler, J. R., 2004, MNRAS 354:212.
  23. Period-Color and Amplitude-Color Relations in Classical Cepheid Variables III: the Large Magellanic Cloud Cepheid Models, by Kanbur, S. & Ngeow, C. C., 2006, MNRAS, 369:705.
    VizieR On-Line Catalogue: Fourier parameters for Cepheid variables
  24. Period-Color and Amplitude-Color Relations in Classical Cepheid Variables IV: the Multi-Phase Relations, by Ngeow, C. C. & Kanbur, S., 2006, MNRAS, 369:723.
  25. Period-Color and Amplitude-Color Relations in Classical Cepheid Variables V: the Small Magellanic Cloud Cepheid models, by Kanbur, S., Ngeow, C. C. & Feiden, G., 2007, MNRAS, 380:819

    Cepheids: Mass-Loss

  26. Testing Mass Loss in Large Magellanic Cloud Cepheids using Infrared and Optical Observations, by Neilson, H., Ngeow, C., Kanbur, S. & Lester, J., 2009, ApJ in-press (arXiv:0810.3001)

    DES Data Management

  27. Cyber-infrastructure to Support Science and Data Management for the Dark Energy Survey, by Ngeow, C. C., Mohr, J., Alam, T., Barkhouse, W., Beldica, C., Cai, D., Daues, G., Plante, R., Annis, J., Huan, L., Tucker, D. & Smith, C., 2006, in "Observatory operations: strategies, processess and system", Proc. of SPIE Vol. 6270, Ed. D. Silva & R. Doxsey, pg. 627023-1.
  28. Photometric Calibration of the Dark Energy Survey, by Tucker, D., Annis, J., Lin, H., Kent, S., Stoughton, C., Peoples, J., Allam, S., Mohr, J., Barkhouse, W., Ngeow, C., Alam, T., Beldica, C., Cai, D., Daues, G., Plante, R., Miller, C., Smith, C., Suntzeff, N. & the Dark Energy Survey Collaboration, 2007, in "The Future of Photometric, Spectrophotometric, and Polarimetric Standardization", ASP Conf. Series Vol 364, Ed. Sterken, C., pg. 187.
  29. The Dark Energy Survey Data Management System, by Joseph J. Mohr, Darren Adams, Wayne Barkhouse, Cristina Beldica, Emmanuel Bertin, Y. Dora Cai, Luiz A. Nicolaci da Costa, J. Anthony Darnell, Gregory E. Daues, Michael Jarvis, Michelle Gower, Huan Lin, Leandro Martelli, Eric Neilsen, Chow-Choong Ngeow, Ricardo L. C. Ogando, Alex Parga, Erin Sheldon, Douglas Tucker, Nikolay Kuropatkin & Chris Stoughton for the Dark Energy Survey Collaboration, 2008, in "Observatory Operations: Strategies, Processes, and Systems II", Proc. of SPIE Vol. 7016, Ed. R. Brissenden & R. Silva, pg. 70160L

My PhD Thesis

Title of the thesis: Investigating the Break of Cepheid Period-Luminosity Relations and its Implications.
Purpose: The aim of this thesis is to investigate the observed breaks in the Cepheid period-luminosity (PL) relations seen in the OGLE LMC Cepheids and its implications for stellar structure, evolution, and cosmology. The work involved in this project includes data collecting and analysis to further characterize the breaks, and pulsation modeling to understand the physical reasons behind such breaks in Cepheid PL relations.

Computer Codes

Some simple c++ programs I wrote for my research (not complete yet):

FITLINE_SIMPLE.cxx - A simple program to fit a straight line to data and find the corresponding slope and zero-point.
INTENSITY_MEAN.cxx - Calculate the intensity mean and phase-weighted intensity mean for the Cepheid observations.
FTEST.cxx - F-test for two regressions vs one regression.

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