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The Postcollapse core of M15 imaged with the HST planetary camera

Lauer, Tod R. and Holtzman, Jon A. and Faber, S. M. and Baum, William A. and Currie, Douglas G. and Ewald, S. P. and Groth, Edward J. and Hester, J. Jeff and Kelsall, T. and Light, Robert M. and Lynds, C. Roger and O'Neill, Earl J., Jr. and Schneider, Donald P. and Shaya, Edward J. and Westphal, James A. (1991) The Postcollapse core of M15 imaged with the HST planetary camera. Astrophysical Journal Letters, 369 (2). L45-L49. ISSN 2041-8205. doi:10.1086/185955.

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We have obtained U-band images of the M15 core with the Planetary Camera of the Hubble Space Telescope. We are able to resolve stars down to the main-sequence turnoff (m_v≈ 19.4) into the cluster center. We use crowded field photometry techniques to decompose M15 into bright resolved stars and a residual component consisting of stars at turnoff brightness or fainter. The residual component comprises 59% of the cluster light and follows a y = -0.71 power-law distribution for r > 1". The residual component flattens off interior to this radius and has a large core with r_c = 2".2 = 0.13 pc. The core size may reflect postcollapse core expansion. The resolved stars have a slightly shallower distribution (y = - 0.53) but have an abrupt overdensity for r < 1".5, which accounts for the unresolved surface brightness cusp at ground resolution. The bright stars do not become more highly concentrated at still smaller radii, however; neither the bright stars nor the residual component form a cusp at subarcsecond resolution. The total central density of light in all components is 8 x 10^5 L_☉ pc^(-3) (U-band). The Peterson, Seitzer, and Cudworth central velocity dispersion implies a high core M/L ≈ 8 (U-band). The existence of a core rather than a cusp at the 0.1 pc scale may imply that the centrally deduced dark matter is in a diffuse form rather than a massive black hole.

Item Type:Article
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URLURL TypeDescription
Faber, S. M.0000-0003-4996-214X
Ewald, S. P.0000-0002-1567-9154
Additional Information:© 1991 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1990 October 17; accepted 1990 November 14. This research was conducted by the WFPC Investigation Definition Team operating under partial support from NASA contract NAS5-25421.
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Subject Keywords:clusters: dynamics, clusters: globular
Issue or Number:2
Record Number:CaltechAUTHORS:20141125-143941746
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Official Citation:The postcollapse core of M15 imaged with the HST planetary camera Authors:Lauer, Tod R.; Holtzman, Jon A.; Faber, S. M.; Baum, William A.; Currie, Douglas G.; Ewald, S. P.; Groth, Edward J.; Hester, J. Jeff; Kelsall, T.; Light, Robert M.; Lynds, C. Roger; O'Neil, Earl J., Jr.; Schneider, Donald P.; Shaya, Edward J.; Westphal, James A. Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 369, March 10, 1991, p. L45-L49.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52157
Deposited By: Ruth Sustaita
Deposited On:26 Nov 2014 16:53
Last Modified:10 Nov 2021 19:21

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