Hubble space telescope NICMOS imaging of the core of M87

Michael R. Corbin, Earl O'Neil, Marcia J. Rieke

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

We present broadband 1.1, 1.6, and 2.2 μm images and a 2.37 μm narrowband image of the inner 19″ of the nearby radio galaxy M87, obtained with the Near Infrared Camera and Multi-Object Spectrometer of the Hubble Space Telescope (HST). The isophotes of the broadband images are almost perfectly circular to within approximately 0″.5 (∼50 pc) of the active nucleus, and an r1/4 law provides a good fit to the galaxy brightness profile at these wavelengths to within the same distance. This result agrees with predictions that the nuclear supermassive black hole will produce a nearly spherical distribution of the surrounding stars within a galaxy crossing time. A difference image formed from the 1.6 μm image and a V-band image obtained with the HST Wide Field Planetary Camera 2 does not show any clear evidence of a physically thick dusty torus around the nucleus, consistent with its lack of strong thermal mid-infrared emission. If such a torus is present, our data indicate its outer radius to be less than 50 pc. The infrared broadband colors and 2.37 μm image (which is sensitive to the strength of the stellar CO absorption) show no gradients to a distance of approximately 5″ (∼400 pc) from the nucleus and are consistent with a population dominated by late M giants, with no evidence of recent star formation. However, the globular clusters in this region are confirmed to consist of stars bluer than the underlying galaxy, indicating a different formation history. The images and associated colors also confirm that the regions beyond the nucleus do not contain strongly concentrated dust, in contrast to many other radio galaxies. In combination with other recent observations, these results indicate that M87 represents the dynamically evolved product of past galaxy mergers and suggest that its nucleus is in the final stages of activity.

Original languageEnglish (US)
Pages (from-to)183-190
Number of pages8
JournalAstronomical Journal
Volume124
Issue number1 1759
DOIs
StatePublished - Jul 1 2002

Keywords

  • Galaxies: individual (M87)
  • Galaxies: nuclei
  • Galaxies: photometry
  • Infrared radiation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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