Circumnuclear Star Clusters in the Galaxy Merger NGC 6240, Observed with Keck Adaptive Optics and HST

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We discuss images of the central {approx} 10 kpc (in projection) of the galaxy merger NGC 6240 at H and K{prime} bands, taken with the NIRC2 narrow camera on Keck II using natural guide star adaptive optics. We detect 28 star clusters in the NIRC2 images, of which only 7 can be seen in the similar-spatial-resolution, archival WFPC2 Planetary Camera data at either B or I bands. Combining the NIRC2 narrow camera pointings with wider NICMOS NIC2 images taken with the F110W, F160W, and F222M filters, we identify a total of 32 clusters that are detected in at least one ... continued below

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Pollack, L K; Max, C E & Schneider, G February 12, 2007.

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We discuss images of the central {approx} 10 kpc (in projection) of the galaxy merger NGC 6240 at H and K{prime} bands, taken with the NIRC2 narrow camera on Keck II using natural guide star adaptive optics. We detect 28 star clusters in the NIRC2 images, of which only 7 can be seen in the similar-spatial-resolution, archival WFPC2 Planetary Camera data at either B or I bands. Combining the NIRC2 narrow camera pointings with wider NICMOS NIC2 images taken with the F110W, F160W, and F222M filters, we identify a total of 32 clusters that are detected in at least one of these 5 infrared ({lambda}{sub c} > 1 {micro}m) bandpasses. By comparing to instantaneous burst, stellar population synthesis models (Bruzual & Charlot 2003), we estimate that most of the clusters are consistent with being {approx} 15 Myr old and have photometric masses ranging from 7 x 10{sup 5} M{sub {circle_dot}} to 4 x 10{sup 7}M{sub {circle_dot}}. The total contribution to the star formation rate (SFR) from these clusters is approximately 10M{sub {circle_dot}} yr{sup -1}, or {approx} 10% of the total SFR in the nuclear region. We use these newly discovered clusters to estimate the extinction toward NGC 6240's double nuclei, and find values of A{sub v} as high as 14 magnitudes along some sightlines, with an average extinction of A{sub v} {approx} 7 mag toward sightlines within {approx} 3-inches of the double nuclei.

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PDF-file: 39 pages; size: 2.4 Mbytes

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  • Journal Name: Astrophysical Journal, vol. 660, no. 1, May 1, 2007, pp. 288-300; Journal Volume: 660; Journal Issue: 1

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  • Report No.: UCRL-JRNL-228148
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 940517
  • Archival Resource Key: ark:/67531/metadc899380

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  • February 12, 2007

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  • Sept. 27, 2016, 1:39 a.m.

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  • Dec. 2, 2016, 9:14 p.m.

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Pollack, L K; Max, C E & Schneider, G. Circumnuclear Star Clusters in the Galaxy Merger NGC 6240, Observed with Keck Adaptive Optics and HST, article, February 12, 2007; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc899380/: accessed November 25, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.