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Detection of the Tip of the Red Giant Branch in NGC 5128

Soria, Roberto and Mould, Jeremy R. and Watson, Alan M. and Gallagher, John S., III and Ballester, Gilda E. and Burrows, Christopher J. and Casertano, Stefano and Clarke, John T. and Crisp, David and Griffiths, Richard E. and Hester, J. Jeff and Hoessel, John G. and Holtzman, Jon A. and Scowen, Paul A. and Stapelfeldt, Karl R. and Trauger, John T. and Westphal, James A. (1996) Detection of the Tip of the Red Giant Branch in NGC 5128. Astrophysical Journal, 465 (1). pp. 79-90. ISSN 0004-637X. doi:10.1086/177403.

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We present a color-magnitude diagram of more than 10,000 stars in the halo of the galaxy NGC 5128 (Centaurus A), based on WFPC2 images through V-band and I-band filters. The position of the red giant branch (RGB) stars is compared with the loci of the red giant branch in six well-studied globular clusters and in the dwarf elliptical galaxy NGC 185; the tip of the RGB is signalled by an observed turn-up in the luminosity function at I≃24.1 ± 0.1 mag; this yields a distance modulus (m - M)_0 = 27.8 ± 0.2 for NGC 5128 (i.e., a distance of 3.6 ± 0.2 Mpc), in agreement with previous determinations based on the planetary nebulae luminosity function and on the surface brightness fluctuations technique. The presence of an intermediate-age stellar population (~5 Gyr) is suggested by the luminosity function of the asymptotic giant branch stars, extending up to I= 22.6 mag (for V - I > 2) and M_(bot) ~ -5 mag; however, the number of these stars constrains the intermediate-age stellar population in the halo of NGC 5128 to be less than ~ 10% of the total. The color distribution at constant I magnitude, albeit affected by the completeness level of our sample, strongly suggests a mean value of [Fe/H] > -0.9 dex, possibly similar to the value found in M31 and higher than that observed in NGC 185. Like the M31 halo, the halo of NGC 5128 exhibits a broad range of levels of chemical enrichment.

Item Type:Article
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URLURL TypeDescription
Soria, Roberto0000-0002-4622-796X
Mould, Jeremy R.0000-0003-3820-1740
Gallagher, John S., III0000-0001-8608-0408
Crisp, David0000-0002-4573-9998
Stapelfeldt, Karl R.0000-0002-2805-7338
Additional Information:© 1996 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1995 October 30; accepted 1996 January 5. Based on observations with the NASA/ESA Hubble Space Telescope. We are grateful to Daya Rawson and Peter Stetson for contributing their expertise in photometry and Neill Reid for star count calculations. We thank Gary Da Costa and Carl Grillmair for critical reading of the manuscript and John Graham and Jay Frogel for their stimulating remarks and suggestions. This research was carried out by the WFPC2 Investigation Definition Team for JPL and was sponsored by NASA through contract NAS7-1260.
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Subject Keywords:galaxies: distances and redshifts, galaxies: individual (NGC 5128), galaxies: stellar content, stars: Hertzsprung-Russell diagram
Issue or Number:1
Record Number:CaltechAUTHORS:20150114-135350590
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Official Citation:Detection of the Tip of the Red Giant Branch in NGC 5128 Soria, R., Mould, J. R., Watson, A. M., Gallagher, J. S., III, Ballester, G. E., Burrows, C. J., , Astrophysical Journal v.465, p.79-90
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53728
Deposited By: Ruth Sustaita
Deposited On:14 Jan 2015 22:42
Last Modified:10 Nov 2021 20:06

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