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Signatures of stellar accretion in MaNGA early-type galaxies

Oyarzún, Grecco A.; Bundy, Kevin; Westfall, Kyle B.; Belfiore, Francesco; Thomas, Daniel; Maraston, Claudia; Lian, Jianhui; Aragón-Salamanca, Alfonso; Zheng, Zheng; Gonzalez-Perez, Violeta; Law, David R.; Drory, Niv; Andrews, Brett H.


Grecco A. Oyarzún

Kevin Bundy

Kyle B. Westfall

Francesco Belfiore

Daniel Thomas

Claudia Maraston

Jianhui Lian

Alfonso Aragón-Salamanca

Zheng Zheng

Violeta Gonzalez-Perez

David R. Law

Niv Drory

Brett H. Andrews


The late assembly of massive galaxies is thought to be dominated by stellar accretion in their outskirts (beyond 2 effective radii R e) due to dry, minor galaxy mergers. We use observations of 1010 passive early-type galaxies (ETGs) within z < 0.15 from SDSS IV MaNGA to search for evidence of this accretion. The outputs from the stellar population fitting codes FIREFLY, pPXF, and Prospector are compared to control for systematic errors in stellar metallicity (Z) estimation. We find that the average radial logZ/Z profiles of ETGs in various stellar mass (M *) bins are not linear. As a result, these profiles are poorly characterized by a single gradient value, explaining why weak trends reported in previous work can be difficult to interpret. Instead, we examine the full radial extent of stellar metallicity profiles and find them to flatten in the outskirts of M * 10 11 M ETGs. This is a signature of stellar accretion. Based on a toy model for stellar metallicity profiles, we infer the ex-situ stellar mass fraction in ETGs as a function of M * and galactocentric radius. We find that ex-situ stars at R∼2R e make up 20% of the projected stellar mass of M * 10 10.5 M ETGs, rising up to 80% for M * 10 11.5 M ETGs.

Journal Article Type Article
Publication Date Aug 1, 2019
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 880
Issue 2
Article Number 111
APA6 Citation Oyarzún, G. A., Bundy, K., Westfall, K. B., Belfiore, F., Thomas, D., Maraston, C., …Andrews, B. H. (2019). Signatures of stellar accretion in MaNGA early-type galaxies. Astrophysical Journal, 880(2), doi:10.3847/1538-4357/ab297c
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