John Moustakas

Galaxy Demographics and Assembly

Galaxies form at the centers of dark matter halos, which merge hierarchically (small to big) to build the largest structures in the universe. Much of my work uses large galaxy surveys to measure how the galaxy population has grown and changed over cosmic time, when and why galaxies stop forming stars, and how the assembly of galaxies is tied to the growth of their dark matter halos.

Highlights

Two panels of galaxy number density versus stellar mass. Left: the star-forming galaxy mass function in shades of blue for redshifts 0.25 to 0.9, all lying on the black present-day curve. Right: the quiescent galaxy mass function in shades of orange, which rises at low stellar masses toward the present day.
Stellar mass functions of star-forming (blue) and quiescent (orange) galaxies from z≈0.9 (lightest shade) to today (black). From Moustakas et al. 2013, ApJ, 767, 50.

Quiescent galaxies have built up from the low-mass end over the last eight billion years

Using redshifts for about 40,000 galaxies from the PRIMUS survey and 170,000 from the Sloan Digital Sky Survey, we measured how the stellar mass function of star-forming and quiescent galaxies has evolved since z≈1. The star-forming population has hardly changed, whereas the number of quiescent galaxies with roughly ten billion solar masses of stars has grown two- to threefold since z≈0.6. Star formation is being shut off at an increasing rate in lower-mass galaxies, and mergers contribute little to the growth of stellar mass over this period.

Selected Papers

  1. Determining the Halo Mass Scale Where Galaxies Lose Their Gas
    G. Rudnick, P. Jablonka, J. Moustakas et al. 2017, ApJ, 850, 181 ADS arXiv DOI
  2. PRIMUS: Effects of Galaxy Environment on the Quiescent Fraction Evolution at z<0.8
    C. Hahn, M. Blanton, J. Moustakas et al. 2015, ApJ, 806, 162 ADS arXiv DOI
  3. The Assembly Histories of Quiescent Galaxies since z = 0.7 from Absorption Line Spectroscopy
    J. Choi, C. Conroy, J. Moustakas et al. 2014, ApJ, 792, 95 ADS arXiv DOI
  4. PRIMUS: Constraints on Star Formation Quenching and Galaxy Merging, and the Evolution of the Stellar Mass Function from z = 0-1 Lead author
    J. Moustakas, A. Coil, J. Aird et al. 2013, ApJ, 767, 50 ADS arXiv DOI
  5. PRIMUS: An Observationally Motivated Model to Connect the Evolution of the Active Galactic Nucleus and Galaxy Populations out to z∼1
    J. Aird, A. Coil, J. Moustakas et al. 2013, ApJ, 775, 41 ADS arXiv DOI
  6. PRIMUS: The Dependence of AGN Accretion on Host Stellar Mass and Color
    J. Aird, A. Coil, J. Moustakas et al. 2012, ApJ, 746, 90 ADS arXiv DOI
  7. Stellar Populations of Elliptical Galaxies in the Local Universe
    G. Zhu, M. Blanton, & J. Moustakas 2010, ApJ, 722, 491–519 ADS arXiv DOI
  8. Physical Properties and Environments of Nearby Galaxies
    M. Blanton & J. Moustakas 2009, ARA&A, 47, 159–210 ADS arXiv DOI
  9. The Late Stellar Assembly of Massive Cluster Galaxies via Major Merging
    K. Tran, J. Moustakas, A. Gonzalez et al. 2008, ApJL, 683, L17 ADS arXiv DOI