A Caltech Library Service

Global Properties of M31's Stellar Halo from the SPLASH Survey. II. Metallicity Profile

Gilbert, Karoline M. and Kalirai, Jason S. and Guhathakurta, Puragra and Beaton, Rachael L. and Geha, Marla C. and Kirby, Evan N. and Majewski, Steven R. and Patterson, Richard J. and Tollerud, Erik J. and Bullock, James S. and Tanaka, Mikito and Chiba, Masashi (2014) Global Properties of M31's Stellar Halo from the SPLASH Survey. II. Metallicity Profile. Astrophysical Journal, 796 (2). Art. No. 76. ISSN 0004-637X.

PDF - Published Version
See Usage Policy.

[img] PDF - Accepted Version
See Usage Policy.


Use this Persistent URL to link to this item:


We present the metallicity distribution of red giant branch (RGB) stars in M31's stellar halo, derived from photometric metallicity estimates for over 1500 spectroscopically confirmed RGB halo stars. The stellar sample comes from 38 halo fields observed with the Keck/DEIMOS spectrograph, ranging from 9 to 175 kpc in projected distance from M31's center, and includes 52 confirmed M31 halo stars beyond 100 kpc. While a wide range of metallicities is seen throughout the halo, the metal-rich peak of the metallicity distribution function becomes significantly less prominent with increasing radius. The metallicity profile of M31's stellar halo shows a continuous gradient from 9 to ~100 kpc, with a magnitude of ~ – 0.01 dex kpc–1. The stellar velocity distributions in each field are used to identify stars that are likely associated with tidal debris features. The removal of tidal debris features does not significantly alter the metallicity gradient in M31's halo: a gradient is maintained in fields spanning 10-90 kpc. We analyze the halo metallicity profile, as well as the relative metallicities of stars associated with tidal debris features and the underlying halo population, in the context of current simulations of stellar halo formation. We argue that the large-scale gradient in M31's halo implies M31 accreted at least one relatively massive progenitor in the past, while the field to field variation seen in the metallicity profile indicates that multiple smaller progenitors are likely to have contributed substantially to M31's outer halo.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Gilbert, Karoline M.0000-0003-0394-8377
Kalirai, Jason S.0000-0001-9690-4159
Guhathakurta, Puragra0000-0001-8867-4234
Beaton, Rachael L.0000-0002-1691-8217
Geha, Marla C.0000-0002-7007-9725
Kirby, Evan N.0000-0001-6196-5162
Majewski, Steven R.0000-0003-2025-3147
Tollerud, Erik J.0000-0002-9599-310X
Bullock, James S.0000-0003-4298-5082
Chiba, Masashi0000-0002-9053-860X
Additional Information:© 2014 American Astronomical Society. Received 2014 April 30; accepted 2014 September 7; published 2014 November 10. Support for this work was provided by NASA through Hubble Fellowship grants 51273.01, and 51316.01 awarded to K.M.G. and E.J.T. by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. P.G., J.S.B., S.R.M., and R.L.B. acknowledge support from collaborative NSF grants AST-1010039, AST-1009973, AST-1009882, and AST-0607726. This project was also supported by NSF grants AST03-07842, AST03-07851, AST06-07726, AST08-07945, and AST10-09882, NASA grant ST-GO-12105.03 through STScI, NASA/JPL contract 1228235, the David and Lucile Packard Foundation, and the F. H. Levinson Fund of the Peninsula Community Foundation (S.R.M., R.J.P., and R.L.B.). E.N.K acknowledges support from the Southern California Center for Galaxy Evolution, a multicampus research program funded by the University of California Office of Research, and partial support from NSF grant AST-1009973. E.J.T. acknowledges support from a Graduate Assistance in Areas of National Need (GAANN) fellowship. R.L.B. acknowledges receipt of the Mark C. Pirrung Family Graduate Fellowship from the Jefferson Scholars Foundation and a Fellowship Enhancement for Outstanding Doctoral Candidates from the Office of the Vice President of Research at the University of Virginia. M.T. acknowledges support from Grant-in-Aid for Scientific Research (25800098) of the Ministry of Education, Culture, Sports, Science, and Technology of Japan. The analysis pipeline used to reduce the DEIMOS data was developed at UC Berkeley with support from NSF grant AST-0071048. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Funding AgencyGrant Number
Space Telescope Science InstituteUNSPECIFIED
NASANAS 5-26555
David and Lucile Packard FoundationUNSPECIFIED
F. H. Levinson Fund of the Peninsula Community FoundationUNSPECIFIED
Southern California Center for Galaxy EvolutionUNSPECIFIED
University of CaliforniaUNSPECIFIED
Graduate Assistance in Areas of National Need (GAANN) fellowshipUNSPECIFIED
Jefferson Scholars FoundationUNSPECIFIED
University of VirginiaUNSPECIFIED
Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan25800098
Subject Keywords:galaxies: groups: individual (M31); galaxies: halos; stars: kinematics and dynamics; techniques: spectroscopic
Issue or Number:2
Record Number:CaltechAUTHORS:20141222-094115048
Persistent URL:
Official Citation:Global Properties of M31's Stellar Halo from the SPLASH Survey. II. Metallicity Profile Karoline M. Gilbert et al. 2014 ApJ 796 76
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53077
Deposited By: Ruth Sustaita
Deposited On:22 Dec 2014 18:26
Last Modified:15 Nov 2019 03:50

Repository Staff Only: item control page