Dr. Kyoung-Soo Lee

I am an assistant professor in the department of Physics and Astronomy at Purdue University, located in West Lafayette, IN.

I am an observational astronomer interested in:

  • how galaxies and clusters of galaxies form and evolve throughout cosmic time.
  • spatial and kinematic structure of distant galaxies
  • different pathways taken by galaxies and how they are linked to the large-scale structure

My research has been featured in multiple media outlets including Sky & Telescope, Astronomy Now, and More details of my research can be found in my curriculum vitae.

Research Highlights

Varied pathways of galaxy formation

I was one of the first to show observational evidence that star formation in the majority of distant galaxies can occur in a `bursty’ manner. As a result, these galaxies flicker throughout cosmic time and are visible only for a fraction of time, as illustrated in the figure (left). My findings are in stark contrast with a continuous and increasing rate of star formation (the right panel) inferred for more luminous and more massive galaxies at the same cosmic epoch. These studies together highlight dramatically different pathways taken by galaxies depending on their masses and large-scale environment.

Witnessing the Early Growth of Galaxy clusters

I discovered and confirmed the largest and most distant cosmic structure (observed when the universe was only 12% of the current age), which will evolve into a most massive class of galaxy cluster by the present day. My group’s comprehensive investigation of this system, including its large-scale structure, a census of galaxy inhabitants, and their physical properties, not only provided an unprecedentedly detailed view of the early stage of cluster formation but also demonstrated the complexity of astrophysical processes governing the formation of its galaxy constituents in dense cosmic environment.

The Physical Origin of Diffuse Lyman Alpha Emission

My group made precision measurements of diffuse hydrogen Lyman α emission around distant galaxies. The figure shows the average image of distant galaxies (at z~3.8) at Lyα wavelengths (top) and ~1700 angstrom, rest-frame (bottom). The right panels show the radially-averaged surface brightness profile of these images. By comparing with theoretical predictions, we demonstrated that ionizing radiation from recently formed stars is the primary power source for this very extended emission. My results pose a serious challenge to the relative importance of gravitational cooling radiation, a popular hypothesis of cosmological origin for the diffuse Lyα phenomenon. This has sharpened the focus of Lyα surface brightness measurement by redefining it as a useful observational tool to constrain the star formation activity within the galaxy.


  1. “How Do Galaxies Trace a Large Scale Structure? A Case study around a massive protocluster at z=3.13”, K. Shi, Y. Huang, K.-S. Lee, J. Toshikawa, K.N. Bowen, N. Malavasi, B. Lemaux, O. Cucciati, O. Le Fevre, A. Dey, Accepted for publication in Astrophysical Journal (2019), in press
  2. “A Census of Galaxy Constituents in a Coma Progenitor Observed at Z>3”, K. Shi, K.-S. Lee, A. Dey, Y. Huang, N. Malavasi, C.-L. Hung, H. Inami, M. Ashby, K. Duncan, R. Xue, N. Reddy, S. Hong, B.T. Jannuzi, M.C. Cooper, A.H. Gonzalez, H.J.A. Rottgering, P.N. Best, C. Tasse, Astrophysical Journal, 871, 83 (2019)
  3. “Statistics of two-point correlation and network topology for Lya emitters at z~2.67”, S. Hong, A. Dey, K.-S. Lee, A.A. Orsi, K. Gebhardt, M. Vogelsberger, L. Hernquist, R. Xue, I. Jung, S.L. Finkelstein, S. Tuttle, M. Boylan-Kolchin, Monthly Notices of Royal Astronomical Society, 483, 3950 (2019)
  4. “Discovery of a Very Large (~20 kpc) Galaxy at z=3.72”, K.-S. Lee, A. Dey, T. Matheson, K. Shi , C.-L. Hung, R. Xue, H. Inami, K.-G. Lee, M. Ashby, B.T. Jannuzi, N. Reddy, S. Hong, W. Mo, N. Malavasi, Astrophysical Journal, 852, 24 (2018)
  5. “CANDELS Multi-wavelength Catalogs: Source Identification and Photometry in the CANDELS Extended Groth Strip”, M. Stefanon et al. including K.-S. Lee, Astrophysical Journal Supplement, 229, 32 (2017)
  6. “UVUDF: UV luminosity functions at the cosmic high-noon”, V. Mehta, C. Scarlata, M. Rafelski, T. Gburek, H.I. Teplitz, A. Alavi, M. Boylan-Kolchin, S. Finkelstein, J.P. Gardner, N. Grogin, A. Koekemoer, P. Kurczynski, B. Siana, A. Codoreanu, D. F. de Mello, K.-S. Lee, and E. Soto, Astrophysical Journal, 838, 29 (2017)
  7. “The Diversity of Diffuse Lyα Nebulae around Star-Forming Galaxies at High Redshift”, R. Xue, K.-S. Lee, A. Dey, H. Inami, S. Hong, N. Reddy, A.H. Gonzalez, B.T. Jannuzi, Astrophysical Journal, 837, 172 (2017)
  8. Spectroscopic Confirmation of a Protocluster at z~3.786”, A. Dey, K.-S. Lee, N. Reddy, M.C. Cooper, H. Inami, S. Hong, A.H. Gonzalez, B.T. Jannuzi, Astrophysical Journal, 823, 11 (2016)
  9. “The galaxy stellar mass function at z=3.5-7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields”, A. Grazian et al. including K.-S. Lee, Astronomy and Astrophysics, 575, 96 (2015)
  10. “The Interstellar Medium and Feedback in the Progenitors of the Compact Passive Galaxies at z~2”, C.C. Williams et al. including K.-S. Lee, Astrophysical Journal, 800, 21 (2015)
  11. “Discovery of a Very Large Structure at z=3.78”, K.-S. Lee, A. Dey, S. Hong, N. Reddy, C. Wilson, B.T Jannuzi, A.H. Gonzalez, Astrophysical Journal, 796, 126 (2014)
  12. “The UV Continuum of z>1 Star-forming Galaxies in the Hubble Ultraviolet UltraDeep Field”, P. Kurczynski, E. Gawiser, M. Rafelski, H. I. Teplitz, V. Acquaviva, T. M. Brown, D.Coe, D. F. de Mello, S. L. Finkelstein, N.A. Grogin,A. M. Koekemoer, K.-S. Lee, C. Scarlata, and B. D. Siana, Astrophysical Journal, 793, 5 (2014)
  13. “A critical assessment of photometric redshift methods: a CANDELS investigation”, T. Dahlen et al. including K.-S. Lee, Astrophysical Journal, 775, 93 (2013)
  14. “CANDELS: The progenitors of compact quiescent galaxies at z~2”, G. Barro et al. including K.-S. Lee, Astrophysical Journal, 765, 104 (2013)
  15. “Probing High-Redshift Galaxy Formation at the Highest Luminosities: New Insights from DEIMOS Spectroscopy”, K.-S. Lee, A. Dey, M.C. Cooper, N. Reddy, B.T. Jannuzi, Astrophysical Journal, 771, 25 (2013)
  16. “The LBT Bootes Field Survey.: I. The Rest-frame Ultraviolet and Near-infrared Luminosity Functions and Clustering of Bright Lyman Break Galaxies at z~3”, F. Bian, X. Fan , L. Jiang, I. McGreer, A. Dey, R. Green , R. Maiolino, F. Walter, K.-S. Lee, R. Dave, Astrophysical Journal, 775, 28 (2013)
  17. “CANDELS Multiwavelength Catalogs: Source Detection and Photometry in the GOODS-South Field”, Y. Guo et al. including K.-S. Lee, Astrophysical Journal Supplement, 207, 24 (2013)
  18. “CANDELS Multiwavelength Catalogs: Source Identification and Photometry in the CANDELS UKIDSS Ultra-deep Survey Field”, A. Galametz et al. including K.-S. Lee, Astrophysical Journal Supplement, 206, 10 (2013)
  19. “Herschel Detection of Dust Emission from UV-Luminous Star-Forming Galaxies at z=3.3-4.3”, K.-S. Lee, S. Alberts, D. Atlee, A. Dey, A. Pope, B.T. Jannuzi, N. Reddy, M.J.I. Brown, Astrophysical Journal, 758, L31 (2012)
  20. “Luminous and High Stellar Mass Candidate Galaxies at z~8 discovered in the CANDELS”, H. Yan et al. including K.-S. Lee, Astrophysical Journal, 761, 177 (2012)
  21. “How Do Star-Forming Galaxies at z>3 Assemble Their Masses?”, K.-S. Lee, H.C. Ferguson, T. Wiklind, T. Dahlen, M.E. Dickinson, M. Giavalisco, N. Grogin, C. Papovich, H. Messias, Y. Guo, L. Lin, Astrophysical Journal, 752, 66 (2012)
  22. “Caught in the Act: The Assembly of Massive Cluster Galaxies at z=1.62”, J. M. Lotz, C. Papovich, S. M. Faber, H. C. Ferguson, N. Grogin, Y. Guo, D. Kocevski, A.M. Koekemoer, K.-S. Lee, D. McIntosh, I. Momcheva, G. Rudnick, A. Saintonge, K.-V. Tran, A. van der Wel, and C. Willmer, Astrophysical Journal, 773, 154 (2012)
  23. “CANDELS: The evolution of Galaxy Rest-frame Ultraviolet Colors from z=8 to z=4”, S.L. Finkelstein, C. Papovich, B. Salmon, K. Finlator, M. Dickinson, H.C. Ferguson, M. Giavalisco, A.M. Koekemoer, N.A. Reddy, R. Bassett, C.J. Conselice, J.S. Dunlop, S.M. Faber, N.A. Grogin, N.P. Hathi, D.D. Kocevski, K. Lai, K.-S. Lee, R.J. McLure, B. Mobasher, and J.A. Newman, Astrophysical Journal, 756, 164 (2012)
  24. “Rest-Frame UV-optically Selected Galaxies at 2.3<z<3.5: Searching for Dusty Star-Forming and Passively-Evolving Galaxies”, Y. Guo, M. Giavalisco, P. Cassata, H. C. Ferguson, C. C. Williams, M. Dickinson, A. Koekemoer, N.A. Grogin, R.-R. Chary, H. Messias, E. Tundo, L. Lin, S.-K Lee, S. Salimbeni, A. Fontana, A. Grazian, D. Kocevski, K.-S. Lee, E. Villanueva, and A. van der Wel., Astrophysical Journal, 749, 149 (2012)
  25. “The Average Physical Properties and Star Formation Histories of the UV-Brightest Star-Forming Galaxies at z~3.7”, K.-S. Lee, A. Dey, N. Reddy, M.J.I. Brown, A.H. Gonzalez, B.T. Jannuzi, M.C. Cooper, X. Fan, F. Bian, E. Glikman, D. Stern, M. Brodwin, A. Cooray, Astrophysical Journal, 733, 99 (2011)
  26. “Extreme Emission-Line Galaxies in CANDELS: Broadband-selected, Starbursting Dwarf Galaxies at z>1”, A. van der Wel et al. including K.-S. Lee, Astrophysical Journal, 741, 111 (2011)
  27. “CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey – The Hubble Space Telescope Observations, Imaging Data Products, and Mosaics”, A.M. Koekemoer et al. including K.-S. Lee, Astrophysical Journal Supplement, 197, 36 (2011)
  28. "CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey”, N.A. Grogin et al. including K.-S. Lee, Astrophysical Journal Supplement, 197, 35 (2011)
  29. “Galaxy Structure and Mode of Star Formation in the SFR-Mass Plane from z~2.5 to z~0.1”, S. Wuyts et al. including K.-S. Lee, Astrophysical Journal, 742, 96 (2011)
  30. “The Number Density and Mass Density of Star-forming and Quiescent Galaxies at z=0.4-2.2”, G.B. Brammer, K.E. Whitaker, P.G. van Dokkum, D. Marchesini, M. Franx, M. Kriek, I. Labbé, K.-S. Lee, A. Muzzin, R.F. Quadri, G. Rudnick, and R. Williams, Astrophysical Journal, 739, 24 (2011)
  31. “The NEWFIRM Medium-band Survey: Photometric Catalogs, Redshifts, and the Bimodal Color Distribution of Galaxies out to z~3”, K.E. Whitaker, I. Labbé, 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, Astrophysical Journal, 735, 86 (2011)
  32. “On the Clustering of Submillimeter Galaxies”, C.C. Williams, M. Giavalisco, C. Porciani, M.S. Yun, A. Pope, K.S. Scott, J.E. Austermann, I. Aretxaga, B. Hatsukade, K.-S. Lee, G.W. Wilson, R. Cybulski, D.H. Hughes, R. Kawabe, K. Kohno, T. Perera, and F.P. Schloerb, Astrophysical Journal, 733, 92 (2011)
  33. “The Faint End of the Quasar Luminosity Function at z~4: Implications for Ionization of the Intergalactic Medium and Cosmic Downsizing”, E. Glikman, S.G. Djorgovski, D. Stern, A. Dey, B.T. Jannuzi, and K.-S. Lee, Astrophysical Journal, 728, 26 (2011)
  34. “The Most Massive Galaxies at 3<z<4 in the NEWFIRM Medium-band Survey: Properties and Improved Constraints on the Stellar Mass Function”, D. Marchesini, K.E. Whitaker, G. Brammer, P.G. van Dokkum, I. Labbe, A. Muzzin, R.F. Quadri, M. Kriek, K.-S. Lee, Astrophysical Journal, 725, 1277 (2010)
  35. “A Detailed Study of Photometric Redshifts for GOODS-South Galaxies”, T. Dahlen, B. Mobasher, M. Dickinson, H.C. Ferguson, M. Giavalisco, N.A. Grogin, Yi. Guo, A. Koekemoer, K.-S. Lee, S.-K. Lee, M. Nonino, A.G. Riess, S. Salimbeni, Astrophysical Journal, 724, 425 (2010)
  36. “The Age Spread of Quiescent Galaxies with the NEWFIRM Medium-band Survey: Identification of the Oldest Galaxies out to z~2”, K.E. Whitaker, P.G. van Dokkum, G. Brammer, M. Kriek, M. Franx, I. Labbe, D. Marchesini, R.F. Quadri, R. Bezanson, G.D. Illingworth, K.-S. Lee, A. Muzzin, G. Rudnick, D.A. Wake, Astrophysical Journal, 719, 1715 (2010)
  37. “The Dead Sequence: A clear Bimodality in Galaxy Colors from z=0 to z=2.5”, G.B. Brammer, K.E. Whitaker, P.G. van Dokkum, D. Marchesini, I. Labbe, M. Franx, M. Kriek, R.F. Quadri, G. Illingworth, K.-S. Lee, A. Muzzin, G. Rudnick, Astrophysical Journal, 706, 173 (2009)
  38. “Mapping the Dark Matter from UV Light at High Redshift: An Empirical Approach to Understand Galaxy Statistics”, K.-S. Lee, M. Giavalisco, C. Conroy, R.H. Wechsler, H.C. Ferguson, R.S. Somerville, M.E. Dickinson, C.M. Urry, Astrophysical Journal, 695, 358 (2009)
  39. “The NEWFIRM Medium-Band Survey: Filter Definitions and First Results”, P.G. van Dokkum, I. Labbe, D. Marchesini, R. Quadri, G. Brammer, K.E. Whitaker, M. Kriek, M. Franx, G. Rudnick, G. Illingworth, K.-S. Lee, A. Muzzin., Publications of the Astronomical Society of the Pacific, 121, 2 (2009)
  40. “A confirmation of the Strong Clustering of Distant Red Galaxies at 2<z<3”, R.F. Quadri, R.J. Williams, K.-S. Lee, M. Franx, P. van Dokkum, and G.B. Brammer, Astrophysical Journal, 685, 1 (2008)
  41. “Spectroscopic Confirmation of an Extreme Starburst at Redshift 4.547”, P. Capak et al. including K.-S. Lee, Astrophysical Journal, 681, 53 (2008)
  42. “Star formation rates in Lyman break galaxies: radio stacking of LBGs in the COSMOS field and the sub-micro-Jansky radio source population”, C.L. Carilli, N. Lee, P. Capak, E. Schinnerer, K.-S. Lee, H. McCracken, M.S. Yun, N. Scoville, V. Smolcic, M. Giavalisco, A. Datta, Y. Taniguchi, C.M. Urry, Astrophysical Journal, 689, 883 (2008)
  43. “The Large-Scale and Small-scale Clustering of Lyman Break Galaxies at 3.5<z<5.5 from the GOODS Survey”, K.-S. Lee, M. Giavalisco, O.Y. Gnedin, R.S. Somerville, H.C. Ferguson, M.E. Dickinson, M. Ouchi, Astrophysical Journal, 642, 63 (2006)
  44. “Lensing Magnification of Supernovae in the GOODS fields”, J. Jonsson, T. Dahlen, A. Goobar, C. Gunnarsson, E. Mortsell, K.-S. Lee, Astrophysical Journal, 639, 991 (2006)
  45. “The Population of BzK-selected ULIRGs at z~2”, E. Daddi, M. Dickinson, R. Chary, A. Pope, G. Morrison, D.M. Alexander, F.E. Bauer, W.N. Brandt, M. Giavalisco, H. Ferguson, K.-S. Lee, B. D. Lehmer, C. Papovich, and A. Renzini, Astrophysical Journal, 631, 13 (2005)
  46. “X-ray Properties of Lyman Break Galaxies in the Great Observatories Origins Deep Survey”, B.D. Lehmer, W.N. Brandt, D.M. Alexander, F.E. Bauer, C.J. Conselice, M.E. Dickinson, M. Giavalisco, N.A. Grogin, A.M. Koekemoer, K.-S. Lee, L.A. Moustakas, D.P. Schneider, Astrophysical Journal, 129, 1 (2005)
  47. “The Hubble Higher z Supernova Search: Supernovae to z~1.6 and Constraints on Type Ia Progenitor Models”, L.-G. Strolger et al. including K.-S. Lee, Astrophysical Journal, 613, 200 (2004)
  48. “Cosmic Variance in the Great Observatories Origins Deep Survey”, R.S. Somerville, K.-S. Lee, H.C. Ferguson, J.P. Gardner, L.A. Moustakas, M. Giavalisco, Astrophysical Journal, 600, L171
  49. “The Great Observatories Origins Deep Survey: Initial Results from Optical and Near-Infrared Imaging”, M. Giavalisco et al. including K.-S. Lee, Astrophysical Journal, 600, L93



A graduate-level course on stellar structure and stellar evolution


An introductory course on cosmology intended for science and engineering majors. The main topic of this course includes observational techniques and their results to map the large scale structure of the universe, historical perspectives of how ideas and data have shaped cosmology throughout modern history, and theoretical models that are in agreement/disagreement with current observations.


This course is intended to introduce science and engineering majors who are comfortable with calculus-based courses to the relevant physics to stars, galaxies, active galaxies, and to cosmology.


Introductory calculus-based physics course using fundamental interactions between atoms to describe Newtonian mechanism, conservation laws, energy quantization, entropy, the kinetic theory of gases, and other related topics of thermodynamics.

Lee Research Group

Current members:

Dr. Ke Shi

Graduate student; Purdue University; graduated May 2019

Yun Huang

Graduate student; Purdue University; 4th year

Luke Dow

Undergraduate student; Purdue University; 2nd year

Kaustub Pavir Anand

Undergraduate student; Purdue University; 2nd year

Kathryn Bowen

Undergraduate student; Purdue University


Past members:

Yuze Lin

Undergraduate student; Purdue University
Spring 2019

Connor Johnston

Undergraduate student; Purdue University

Adrian Helming-Cornell

Undergraduate student; Purdue University

Bob Caddy

Undergraduate student; Purdue University

Liam Stout

Undergraduate student; St. Andrews University (UK)

Samuel Frampton

Undergraduate student; Lancaster University (UK)

Guobao Tang

Undergraduate student; l’Universite’ de Paris (France)
Summer 2015

Gregory Neeser

Undergraduate student; Purdue University

Christian Wilson

Undergraduate student; Purdue University


Email: soolee {at}
Office phone: (765) 494-3047
Office: PHYS 251

Mailing address:
Department of Physics and Astronomy
Purdue University
West Lafayette, IN

Copyright 2019 - Kyoung-Soo Lee.
All rights reserved