Bio

I am a Rubin Postdoctoral Fellow at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University and SLAC National Accelerator Laboratory.

I study the large scale structure of the universe to extract information about fundamental physics and our cosmic origins. I am particularly interested in the high-redshift universe and using Lyman-break Galaxies (LBGs) and CMB lensing to constrain cosmology in the matter-dominated era. I created and lead the LBG Topical Team of the Dark Energy Science Collaboration (DESC) of the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST). I also work on DESC's weak lensing analysis, particularly on pipelines, simulations, and validation for photo-z estimation and on photometric error modeling for simulated multi-survey catalogs.

I am also a member of the Rubin Observatory's active optics team. The active optics system applies real-time corrections to the telescope's optical alignment and mirror figure to optimize image quality for precision science, and is particularly vital for weak lensing and large-scale structure cosmology. I am primarily focused on wavefront estimation (i.e., inferring the presence of optical aberrations from Rubin images) and commissioning the active optics control system. I have spent many nights on the summit observing with and commissioning the Rubin Observatory.

I received my PhD at the University of Washington, advised by Prof. Andy Connolly. Before that, I completed my undergraduate studies at Duke University, where I was a Duke Faculty Scholar working with Prof. Kate Scholberg in the Duke Neutrino and Cosmology Group.

In my free time I enjoy alpine climbing, backcountry skiing, and watching way too many movies.

Note that I have a double name and go by "John Franklin" or "JF", not just "John".

Professional Education

  • B.S., Duke University, Physics (2019)
  • M.S., University of Washington, Physics (2020)
  • Ph.D., University of Washington, Physics (2025)

Stanford Advisors

Contact

  • Academic
    jfcren@stanford.edu
    University - Scholar Department: Physics Position: Postdoctoral Scholar

Additional Info

Links

Current Research and Scholarly Interests

I study the large scale structure of the universe to extract information about fundamental physics and our cosmic origins. I am particularly interested in the high-redshift universe and using Lyman-break Galaxies (LBGs) and CMB lensing to constrain cosmology in the matter-dominated era. I created and lead the LBG Topical Team of the Dark Energy Science Collaboration (DESC) of the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST).

I also work on the Rubin Observatory's active optics system, which applies real-time corrections to the telescope's optical alignment and mirror figure to optimize image quality for precision science. I am particularly focused on wavefront estimation (i.e., inferring the presence of optical aberrations from Rubin images) and commissioning the active optics control system. I have spent many nights on the summit observing with and commissioning the Rubin Observatory.

All Publications

  • Impact of survey spatial variability on galaxy redshift distributions and the cosmological 3 x 2-point statistics for the Rubin Legacy Survey of Space and Time (LSST) MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY Hang, Q., Joachimi, B., Charles, E., Crenshaw, J., Larsen, P., Malz, A., Schmidt, S., Yan, Z., Zhang, T., LSST Dark Energy Sci Collaboration 2024; 535 (4): 2970-2997

    View details for DOI 10.1093/mnras/stae2519

    View details for Web of Science ID 001364222200001

  • The Active Optics System on the Vera C. Rubin Observatory: Optimal Control of Degeneracy among the Large Number of Degrees of Freedom ASTROPHYSICAL JOURNAL Homar, G., Kahn, S. M., Meyers, J. M., Crenshaw, J., Thomas, S. J. 2024; 974 (1)

    View details for DOI 10.3847/1538-4357/ad6cdc

    View details for Web of Science ID 001328744900001

  • Probabilistic Forward Modeling of Galaxy Catalogs with Normalizing Flows ASTRONOMICAL JOURNAL Crenshaw, J., Kalmbach, J., Gagliano, A., Yan, Z., Connolly, A. J., Malz, A. I., Schmidt, S. J., LSST Dark Energy Science Collaboration 2024; 168 (2)

    View details for DOI 10.3847/1538-3881/ad54bf

    View details for Web of Science ID 001275377900001

  • Improving Photometric Redshift Estimates with Training Sample Augmentation ASTROPHYSICAL JOURNAL LETTERS Moskowitz, I., Gawiser, E., Crenshaw, J., Andrews, B. H., Malz, A. I., Schmidt, S., LSST Dark Energy Sci Collaboration 2024; 967 (1)

    View details for DOI 10.3847/2041-8213/ad4039

    View details for Web of Science ID 001222012500001

  • Using AI for Wave-front Estimation with the Rubin Observatory Active Optics System ASTRONOMICAL JOURNAL Crenshaw, J., Connolly, A. J., Meyers, J. E., Kalmbach, J., Homar, G., Ribeiro, T., Suberlak, K., Thomas, S., Tsai, T. 2024; 167 (2)

    View details for DOI 10.3847/1538-3881/ad1661

    View details for Web of Science ID 001153613400001

  • Advancing the Vera C. Rubin Observatory Active Optics Control System Homar, G., Meyers, J. M., Thomas, S. J., Kahn, S. M., Connolly, A. J., Crenshaw, J., Kalmbach, J., Suberlak, K., Polen, R., Tsai, T., Ribeiro, T., Tighe, R., Rodeghiero, G., Canestrari, R., Giro, E., Niell, D., Kubanek, P., Rosignoli, L., Rivera, M., Sebag, J., Mills, D., Zorzi, P., Lopez, J., Jimenez, D., Ordenes, I., Fabrega, J. edited by Marshall, H. K., Spyromilio, J., Usuda, T. SPIE-INT SOC OPTICAL ENGINEERING. 2024

    View details for DOI 10.1117/12.3019361

    View details for Web of Science ID 001327600100100

  • The simulated catalogue of optical transients and correlated hosts (SCOTCH) MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY Lokken, M., Gagliano, A., Narayan, G., Hlozek, R., Kessler, R., Crenshaw, J., Salo, L., Alves, C. S., Chatterjee, D., Vincenzi, M., Malz, A., Lsst Dark Energy Sci Collaboration 2023; 520 (2): 2887-2912

    View details for DOI 10.1093/mnras/stad302

    View details for Web of Science ID 000941753400001

  • The Sensitivity of GPz Estimates of Photo-<i>z</i> Posterior PDFs to Realistically Complex Training Set Imperfections PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC Stylianou, N., Malz, A. I., Hatfield, P., Crenshaw, J., Gschwend, J. 2022; 134 (1034)

    View details for DOI 10.1088/1538-3873/ac59bf

    View details for Web of Science ID 000788286800001

  • Learning Spectral Templates for Photometric Redshift Estimation from Broadband Photometry ASTRONOMICAL JOURNAL Crenshaw, J., Connolly, A. J. 2020; 160 (4)

    View details for DOI 10.3847/1538-3881/abb0e2

    View details for Web of Science ID 000576410200001

https://orcid.org/0000-0002-2495-3514