• Megan Donahue
  Physics and Astronomy Department
  Michigan State University
  East Lansing, Michigan 48824-2320

• E-mail: donahueATpa.msu.edu
• Phone: 1-517-884-5618
• FAX: 1-517-353-4500

Professional Interests:

• Entropy distributions in intracluster gas. Entropy reveals a cluster's past: where was heat deposited, how fast will the gas cool. Sorting out how entropy is distributed in the intergalactic gas in clusters is a key to sorting out how intracluster gas evolves. I use Chandra and XMM data to measure entropy distributions in clusters.
• Hubble Space Telescope observations of distant galaxies: galaxy morphologies in the field have been well studied with large programs such as GOODS. We have an HST snapshot program to collect high-resolution images of galaxies in denser environments: the clusters. This program generates public data that will be used to study the effect of environment on galaxy morphologies, the signature of dark matter on the statistics of strong gravitational lensing, and the overall effect of large scale structure on the signature of weak lensing.
• Star formation in the brightest galaxies in clusters of galaxies, or BCGs, for Brightest Cluster Galaxies. These galaxies pose a real problem for galaxy formation models. They're big, but they're not big enough. They're redder than the theorists predict, but can be bluer than the observers expect.
• Distant clusters of galaxies. Cluster evolution tells us a lot about the matter density of the universe because the assembly and formation of these large structures are governed by gravitational physics. I'm interested in cluster evolution, which means I'm interested not only in finding clusters but HOW they're found, because any bias in HOW they are found can lead to a bias in our conclusions about them.
• Intergalactic gas: metallicity, distribution, physics. Is it really where most of the baryons are hiding? What is the effect of supernovae and radio galaxies on this gas?
• Cooling flows: models and observational tests. Strange things are afoot in cluster cores and I'd like to sort it out. I'd also like to campaign to separate the phenomenon from the model and stop calling the phenomenon "cooling flows." Wouldn't you? We have Chandra, Spitzer, SOAR (the MSU Chilean telescope) programs to study cooling flows and clusters.

  Get an Astrophysics Data System listing of my recent papers by clicking below:

  My Last 100 Papers

  Some recent papers:

  HST NICMOS and WFPC2 Observations of Vibrationally Excited Molecular Hydrogen in Cluster Cooling Flow Nebulae (PostScript, gzipped)

  M. Donahue, J. Mack, G. M. Voit, W. Sparks, R. Elston, P. R. Maloney , 2000, ApJ, accepted Dec 2000. We detect and discuss the implications of extended vibrationally-excited molecular hydrogen in three central galaxies in clusters of galaxies: NGC1275, Abell 2597, and PKS0745-191. The molecular gas is not cooling in a cooling flow. The gas is likely to be excited by the UV emission from hot stars. This hypothesis is testable with IR spectra and FIR imaging. Shocks do not play an important role in exciting this emission, despite the morphology of the molecular and optical emission-line emitting filaments, which appear to wrap around the lobes of the radio sources.

  Omega-Matter from the Temperature-Redshift Distribution of EMSS Clusters of Galaxies

  M. Donahue and G. M. Voit, 1999, ApJ Letters, Oct 1. This is the major result from our ASCA temperature survey of the most distant EMSS clusters of galaxies. We examine the statistics and the systematics and conclude that we can solidly rule out Omega=1, with only a handful of clusters with z=0.5-0.83. That's all you need.

  The Second Most Distant Cluster of Galaxies in the EMSS

  M. Donahue, G. M. Voit, C. Scharf, I. M. Gioia, C. R. Mullis, J. P. Hughes, J. T. Stocke, 1999, accepted to ApJ (gzipped), Dec 20 1999. This paper also summarizes our ASCA EMSS survey results and places constraints on the evolution of the cluster Lx-Tx relation. Short answer: it doesn't evolve much!

  Temperature and Metallicity of a Massive X-ray Cluster of Galaxies

  M. Donahue, ApJ, 468, 79.

  Problems with Cold Clouds in Cooling Flows

  G. Mark Voit and M. Donahue, ApJ, 452, 164. This paper is a really nice analysis of the consequences of cold clouds in cooling flows. It does indicate the limitations of standard photoionization models. This paper is a must for fans of Mike Shull's Internal Processes class .

  Low Surface Brightness H-Alpha Observations of Local Intergalactic Hydrogen Clouds

  M. Donahue, G. Aldering, J. Stocke , ApJL, 450, L45. Very high sensitivity to low surface brightness observations can be made through narrow interference filters if the night is good (clear and moonless) and the CCD *behaves*! We have the proof!

• Preprints for ftp (Press SHIFT and select for download):

  A Very Hot, Massive X-ray Cluster at Redshift 0.8: Trouble for Omega_0 = 1 and plate

  M. Donahue, G. M. Voit, I. M. Gioia, G. Luppino, J. Hughes, J. Stocke , as accepted to the ApJ .

  Origins of Clusters and the Intracluster Medium

  M. Donahue, Review Talk at the Origins Workshop in Estes Park in May, 1997.

  Emission Line Nebula In Cluster Cooling Flows

  Megan Donahue and G. Mark Voit, Haifa proceedings on Cluster Cooling Flows, August, 1996.

  Personal Interests

  • Running, track and field
  • Orienteering: A Major Athletic Accomplishment : and sometimes you just have to show up!
  • Movies
  • Volleyball
  • Skiing, hiking, anything in the mountains...

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  Most recent addition to the family: Angela Voit, born Sept 10, 2002! Sept 2002 photos of ANGELA!

  Last updated 25 Sept 2000! Borrowed a digital camera. Pictures of my family