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A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy. V. Variation of the Metallicity Distribution Function along the Sagittarius Stream

Chou, Mei-Yin and Majewski, Steven R. and Cunha, Katia and Smith, Verne V. and Patterson, Richard J. and Martínez-Delgado, David and Law, David R. and Crane, Jeffrey D. and Muñoz, Ricardo R. and Garcia López, Ramón and Geisler, Doug and Skrutskie, Michael F. (2007) A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy. V. Variation of the Metallicity Distribution Function along the Sagittarius Stream. Astrophysical Journal, 670 (1). pp. 346-362. ISSN 0004-637X. doi:10.1086/522483.

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We present reliable measurements of the metallicity distribution function (MDF) at different points along the tidal stream of the Sagittarius (Sgr) dwarf spheroidal (dSph) galaxy, based on high-resolution, echelle spectroscopy of candidate M giant members of the Sgr system. The Sgr MDF is found to evolve significantly from a median [Fe/H] ~ -0.4 in the core to ~-1.1 dex over a Sgr leading arm length representing ~2.5-3.0 Gyr of dynamical (i.e., tidal stripping) age. This is direct evidence that there can be significant chemical differences between current dSph satellites and the bulk of the stars they have contributed to the halo. Our results suggest that Sgr experienced a significant change in binding energy over the past several gigayears, which has substantially decreased its tidal boundary across a radial range over which there must have been a significant metallicity gradient in the progenitor galaxy. By accounting for MDF variation along the debris arms, we approximate the MDF Sgr would have had several gigayears ago. We also analyze the MDF of a moving group of M giants we previously discovered toward the north Galactic cap. These objects have the opposite radial velocities to the infalling Sgr leading arm stars there, and we propose that most of them represent Sgr trailing arm stars overlapping the Sgr leading arm in this part of the sky. If so, these trailing arm stars further demonstrate the strong MDF evolution within the Sgr stream.

Item Type:Article
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URLURL TypeDescription DOIArticle
Majewski, Steven R.0000-0003-2025-3147
Martínez-Delgado, David0000-0003-3835-2231
Law, David R.0000-0002-9402-186X
Additional Information:© 2007 The American Astronomical Society. Received 2006 May 3; accepted 2007 August 9. We gratefully acknowledge support by NSF grant AST 03- 07851, NASA JPL contract 1228235 and the David and Lucile Packard Foundation as well as Frank Levinson through the Peninsular Community Foundation. V. V. S. and K. C. also express thanks for support from the NSF via grant AST 03-07534 and the Association of Universities for Research in Astronomy (AURA), Inc., through GF-1006-00.D.G. gratefully acknowledges support from the Chilean Centro de Astrofısica FONDAP No. 15010003. The author thanks Jon Fulbright for kindly providing the MIKE spectrum of Arcturus. Parts of this paper were written while S. R. M., K. C., and V. V. S. participated in the Deconstructing the Local Group workshop held at the Aspen Center for Physics in 2006 June. Finally, we appreciate helpful comments from the anonymous referee.
Funding AgencyGrant Number
NSFAST 03-07851
David and Lucile Packard FoundationUNSPECIFIED
Peninsular Community FoundationUNSPECIFIED
NSFAST 03-07534
Association of Universities for Research in Astronomy (AURA)GF-1006-00
Fondo de Financiamiento de Centros de Investigación en Áreas Prioritarias (FONDAP)15010003
Subject Keywords:galaxies : evolution; galaxies : interactions; Galaxy : halo; Local Group
Issue or Number:1
Record Number:CaltechAUTHORS:20091116-101106007
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Official Citation:A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy. V. Variation of the Metallicity Distribution Function along the Sagittarius Stream Mei-Yin Chou, Steven R. Majewski, Katia Cunha, Verne V. Smith, Richard J. Patterson, David Martínez-Delgado, David R. Law, Jeffrey D. Crane, Ricardo R. Muñoz, Ramón Garcia López, Doug Geisler, and Michael F. Skrutskie 2007 ApJ 670 346-362 doi: 10.1086/522483
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16714
Deposited By: Tony Diaz
Deposited On:25 Nov 2009 21:31
Last Modified:08 Nov 2021 23:29

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