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Three-dimensional cross power spectrum of the 21cm emission measured at the Green Bank Telescope and the optical density field traced by the WiggleZ redshift survey. Negative points are shown with reversed sign and a thin line. The solid line is the mean of simulations based on the empirical non-linear model of Blake et al. (2011) processed by the same pipeline. The overall amplitude is consistent with a measurement of Omega_HI~4*10^(-4) at z=0.8, similar to the value measured at z=0.
21cm brightness fluctuation at z=0.8 in cross-correlation
A cross-correlation measurement of 21-cm emission measured by the Green Bank Telescope, and the optical galaxies measured by the DEEP2 galaxy survey.
An intensity map of hydrogen 21-cm emission at redshift z ≈ 0.8
Average power spectrum in units of K 2 of all combinations of days, excluding December 11, as a function of the multipole moment l. Each point is shown with a 2σ upper limit derived from a bootstrap error analysis, which is in most cases smaller than the size of the point. The points are logarithmically spaced as described in the text, from left to right covering the ranges 377 < l < 578, 578 < l < 899 and 899 < l < 1414. Triangles are the power before subtracting foregrounds, diamonds are after 8 MHz mean subtraction, squares are after 2 MHz mean subtraction and circles are after 0.5 MHz subtraction. The curved solid line is the theoretical EoR signal from Jelic et al. (2008), and the dashed line is the theoretical EoR signal ´ with a cold absorbing IGM as described in the text.
The GMRT Epoch of Reionization experiment: a new upper limit on the neutral hydrogen power spectrum at z ≈ 8.6
Chang, Tzu-Ching
Assistant Research Fellow
photo of Chang, Tzu-Ching
Office: ASMAB 1420
TEL: +886-2-2366-5457
FAX: +886-2-2367-7849

Education and Positions

  • Assistant Research Fellow, ASIAA (2010 ~ present)
  • CITA-ASIAA Postdoctoral Fellow, Canadian Institute for Theoretical Astrophysics and ASIAA (2006 ~ 2010)
  • TAC Fellow, UC Berkeley (2003 ~ 2006)
  • Ph.D, Astrophysics, Columbia University (2003)
  • B.S., Physics, National Taiwan University (1997)

Honors & Awards

  • TWAS Young Affiliate (2012 ~ 2016)
  • Academia Sinica Distinguished Postdoctoral Fellowship (2007 ~ 2009)
  • TAC Fellowship, UC Berkeley (2003)

Research Interests

21-cm Cosmology; Cosmic Reionization; Gravitational Lensing; Large-scale Structure

Recent Journal Papers

  1. Anthony Pullen, (Tzu-Ching Chang), Olivier Dore, Adam Lidz, "Cross-correlations as a carbon monoxide detector" , ASTROPHYSICAL JOURNAL, 2012, submitted [SCI]
  2. J. C. Pober, A. R. Parsons, D. R. DeBoer, P. McDonald, M. McQuinn, J. E. Aguirre, Z. Ali, R. F. Bradley, (T.-C. Chang), M. F. Morales, "The Baryon Acoustic Oscillation Broadband and Broad-beam Array: Design Overview and Sensitivity Forecasts" , ASTRONOMICAL JOURNAL, 2012, submitted [SCI]
  3. K. W. Masui, E. R. Switzer, N. Banavar, K. C. Bandura, Blake, L. M. Calin, (T.-C. Chang), X. Chen, Y.-C. Li, Y.-W. Liao, "Measurement of 21 cm brightness fluctuations at z ~ 0.8 in cross-correlation" , Astrophysical Journal Letters: 763(1), L20, 2013-01 [SCI] (Fulltext)
  4. Elisabeth Krause, (Tzu-Ching Chang), Olivier Doré, Keiichi Umetsu, "The Weight of Emptiness: The Gravitational Lensing Signal of Stacked Voids" , Astrophysical Journal Letters: 762(2), L20, 2013-01 [SCI]
  5. Lidz A; Furlanetto SR; Oh SP; Aguirre J; Chang T-C;et al. , "Intensity Mapping with Carbon Monoxide Emission Lines and the Redshifted 21 cm Line" , ASTROPHYSICAL JOURNAL: 741(2), 70, 2011-11 [SCI] (Fulltext)
  6. Paciga G; Chang T-C; Gupta Y; et al. , "The GMRT Epoch of Reionization experiment: a new upper limit on the neutral hydrogen power spectrum at z≈ 8.6" , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: 413(2), 1174-1183, 2011-05 [SCI] (Fulltext)
  7. Alvarez MA; Pen UL; Chang T-C, "Enhanced Detectability of Pre-reionization 21-cm Structure" , ASTROPHYSICAL JOURNAL: 723(1), L17-L21, 2010-11 [SCI] (Fulltext)
  8. Chang TC; Pen UL; Bandura K; Peterson JB, "An intensity map of hydrogen 21-cm emission at redshift" , NATURE: 466(7305), 463-465, 2010-07 [SCI] (Fulltext)
  9. Pen UL; Chang TC; Hirata CM; et al., "The GMRT EoR experiment: limits on polarized sky brightness at 150 MHz" , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: 399(1), 181-194, 2009-10 [SCI] (Fulltext)
  10. Pen U-L; Staveley-Smith L; Peterson J; Chang T-C, "First Detection of Cosmic Structure in the 21-cm Intensity Field" , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: 394(1), L6-L10, 2009-03 [SCI] (Fulltext)
  11. Chang T-C; Pen U-L; Peterson JB; McDonald P, "Baryon Oscillation Intensity Mapping of Dark Energy" , PHYSICAL REVIEW LETTERS: 100(9), Art. No. 091303, 2008-03 [SCI] (Fulltext)
  12. Cohn JD; Chang T-C, "Source mergers and bubble growth during reionization" , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: 374(1), 72-94, 2007-01 [SCI] (Fulltext)
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