Space Astrophysics Laboratory

Illuminating the Invisible Cosmic Web

Prof. Christopher Martin

California Institute of Technology

Space Astrophysics Laboratory

Our laboratory is engaged in an experimental and observation program to image emission from the intergalactic medium (IGM), the location of most of the baryons in the Universe. Ultimately, our goal is to understand how gas from the IGM flows into the halos of galaxies, the "Circum-Galactic Medium" [CGM], and how it flows out of galaxies back into the CGM and IGM. The cosmic evolution of galaxies is driven by the flow of gas into and out of them. Our long-term goals are (1) to understand the history of cosmic gas accretion into galaxies; (2) the feedback of energy, gas, and heavy elements into the IGM from galactic scale and black hole winds; (3) to locate galaxies withiin the baryonic cosmic web; and (4) using these observations combined with numerical simulations, to assemble a predictive theory for baryonic structure formation.

We are developing new instruments that are designed to image the very low surface brightness emission from the IGM and CGM, "Dim Matter". These instruments include the Palomar Cosmic Web Imager, the Keck Cosmic Web Imager and its red arm the Keck Cosmic Reionization Mapper, and the FIREBALL-2 and HALO balloon and explorer. Using these instruments we will be able to detect and map CGM and IGM emission from the epoch of Reionization (z=8) to the local Universe (z=0). For the space UV, we need to develop new, high efficiency photon counting detectors and wide field imaging spectrometers to enable detecting the local cosmic web in emission.

We are developing techniques for interpreting the data from these instruments, and observational techniques to unravel the star formation history in galaxies. One of our principal goals is to relate the star formation history of galaxies with the properties of their halos (CGM).

Circum-Galactic and Intergalactic Medium

Understanding the distribution of matter, energy, rotation, and heavy elements in galaxy halos. Determining the importance of cold and hot gas accretion and outflows in determining the evolution of galaxies. Connecting CGM/Halo properties with galaxy properties in order to understand the co-evolution of galaxies and their gas halos. Using KCWI, PCWI, FIREBALL-2, HALO.

The complex flow of matter, energy, and metals between galaxies and CGM.

Papers: Martin+14a; Martin+14b; Martin+15; Martin+16; Martin+19; O'Sullivan+20

Transition galaxies

GALEX discovered a new class of galaxies undergoing a transition from (or to) the star-forming main sequence to passive evolution. We have developed a new observable metric, Star Formation Acceleration, in order to track the evolution of galaxies over the galaxy "HR-diagram" (the stellar mass - star formation rate diagram). The long-term goal is to connect this evolution to the properties of the baryonic and dark matter halos that the galaxies live in. Using GALEX, KCWI, PCWI, HALO, SDSS, other surveys.

Papers: Wyder+07; Schiminovich+07; Martin+07a; Krause+13; Martin+17; Darvish+18

Figure from Martin+17: A New Methodology for Galaxy Physical Parameters

Keck Cosmic Reionization Mapper (KCRM)

Red channel for KCWI focussed on searching for emission from IGM gas undergoing reionization in order to determine the sources and history of re-ionization. In detailed design phase.

Keck Cosmic Web Imager (KCWI)

Keck instrument for faint, integral field spectroscopy with flexible (low to high) spectral and spatial resolution and precision sky subtraction, in the optical band. Successful first light April 11, 2017. Now a popular dark-time instrument for imaging spectroscopy.


Faint Intergalactic mediuum Redshifted Emission Balloon.

High spectral resolution instrument for detecting low surface brightness emission from IGM, CGM. Multi-object UV spectroscopy. Major collaboration with France. Funded by NASA, CNES, CNRS. Partners: Caltech, CNES, Laboratorie Astrophysique Marseille, Columbia University, University of Arizona

Papers: Hamden+20; Kyne+20; Picouet+20

HALO Galaxy-Halo Co-evolution Explorer

Galaxy-Halo Co-evolution explorer. MIDEX concept to map low redshift baryonic and dark matter halos using UV emission lines, and explore the low surface brightness UV universe, in concept development.

GALEX: The Galaxy Evolution Explorer

a NASA Small Explorer Mission performed imaging and spectroscopic surveys in the ultraviolet, launched April 28, 2003. Included major guest Investigator program. Principal Investigator. Science includes galaxy evolution, star formation physics, black hole evolution and its effect on galaxy evolution, stellar and interstellar astrophysics. Mission ended 2013, but an active archival research program continues.

Palomar Cosmic Web Imager (PCWI)

High spectral resolution instrument for detecting low surface brightness emission from the ground. Designed to detect and map for the first time emission from the Intergalactic medium (IGM). Prototype for KCWI. Now a popular general use instrument. (Palomar, Funded by NSF and Caltech)

Recent Publications

  • Hoadley, K., Martin, D.C., Metzger, B., Seibert, M. 2020, A blue ring nebula from a stellar merger several thousand years ago, Nature, 587, 387.

  • O'Sullivan, D., Martin, D. C., Matuszewski, M. et al. 2020, The FLASHES Survey I: Integral Field Spectroscopy of the CGM around 48 z=2.3−3.1 QSOs, Ap.J., 894, 3. link

  • Martin, D. C., O’Sullivan, D., Matuszewski, M., et al., 2019. Multi-Filament Inflows Fuel Young Star Forming Galaxies, Nature Astronomy, 3, 822. link

  • Cai, Z., Hamden, E., Matuszewski, M., Prochaska, J. X., Li, Q., Cantalupo, S., Arrigoni Battaia, F., Martin, C., Neill, J. D., O’Sullivan, D., Wang, R., Moore, A., & Morrissey, P., 2018. Keck/Palomar Cosmic Web Imagers Reveal an Enormous Lyα Nebula in an Extremely Overdense Quasi-stellar Object Pair Field at z = 2.45, Ap.J.L., 861, L3. link

  • Darvish, B., Scoville, N. Z., Martin, C., Mobasher, B., Diaz-Santos, T., & Shen, L., 2018. Similar Scaling Relations for the Gas Content of Galaxies Across Environments to z ∼ 3.5, Ap.J., 860, 111. link

  • Morrissey, P., Matuszewski, M., Martin, D. C., et al., 2018. The Keck Cosmic Web Imager, Ap.J., 864, 93. link

  • Darvish, B., Martin, D. C., Goncalves, T., Mobasher, B., Scoville, N. Z. and Sobral, D., 2018. Quench- ing or Bursting: The Role of Stellar Mass, Environment, and Specific Star Formation Rate to z∼1, Ap.J., 853, 155. link

  • Martin, D. C., Gonc ̧alves, T. S., Darvish, B., Seibert, M., Schiminovich, D., 2017. Quenching or Bursting: Star Formation Acceleration–A New Methodology for Tracing Galaxy Evolution, Ap.J., 842, 20. link

  • Nikzad, S., Jewell, A. D., Hoenk, M. E., et al. 2017 High Efficiency UV/Optical/NIR Detectors for Large Aperture Telescopes and UV Explorer Missions: Development of and Field Observations with Delta-doped Arrays’, Journal of Astronomical Telescopes, Instruments, and Systems, 3, 036002 link

  • Martin, D. C., Matuszewski, M., Morrissey, P., et al. 2016, A Newly Forming Cold Flow Protogalactic Disk, a Signature of Cold Accretion from the Cosmic Web, Ap.J.L., 824, L5. link

  • Martin, D. C., Matuszewski, M., Morrissey, P., Moore, A., Cantalupo, S., Prochaska, J. X., Chang, D. 2015, A Giant Protogalactic Disk Linked to the Cosmic Web, Nature, 524, 192. link

  • Hamden, E.~T., Jewell, A.~D., Shapiro, C.~A., et al. 2016, Charge-coupled devices detectors with high quantum efficiency at UV wavelengths, Journal of Astronomical Telescopes, Instruments, and Systems, 2, 036003 link


Marty Crabill -- Senior Research Technician

Behnam Darvish -- Postdoctoral Fellow

Pradip Gatkine -- David & Ellen Lee Prize Postdoctoral Fellow in Experimental Physics

Keri Hoadley -- David & Ellen Lee Prize Postdoctoral Fellow in Experimental Physics

Zeren Lin -- Graduate Research Assistant

Christopher Martin -- Professor of Physics

Matt Matuszewski -- Senior Staff Scientist

Debbie MIles -- Administrative Assistant

Don Neill -- Senior Scientific Software Engineer


Ay 127 -- Cosmology and Galaxy Evolution

Ay 122a -- Observations and Instrumentation

Ph 1bc(Prac) -- Introduction to Electricity and Magnetism

Ph 2a -- Waves and Radiation

Ph 2b -- Introduction to Quantum Mechanics

Curriculum Vitae

Jan 2021 CV

Image credit: Illustris TNG Collaboration