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The Stellar Populations of Two Ultra-diffuse Galaxies from Optical and Near-infrared Photometry

Pandya, Viraj and Romanowsky, Aaron J. and Laine, Seppo and Brodie, Jean P. and Johnson, Benjamin D. and Glaccum, William and Villaume, Alexa and Cuillandre, Jean-Charles and Gwyn, Stephen and Krick, Jessica and Lasker, Ronald and Martín-Navarro, Ignacio and Martínez-Delgado, David and van Dokkum, Pieter (2018) The Stellar Populations of Two Ultra-diffuse Galaxies from Optical and Near-infrared Photometry. Astrophysical Journal, 858 (1). Art. No. 29. ISSN 1538-4357. doi:10.3847/1538-4357/aab498.

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We present observational constraints on the stellar populations of two ultra-diffuse galaxies (UDGs) using optical through near-infrared (NIR) spectral energy distribution (SED) fitting. Our analysis is enabled by new Spitzer-IRAC 3.6 and 4.5 μm imaging, archival optical imaging, and the prospectorfully Bayesian SED fitting framework. Our sample contains one field UDG (DGSAT I), one Virgo cluster UDG (VCC 1287), and one Virgo cluster dwarf elliptical for comparison (VCC 1122). We find that the optical–NIR colors of the three galaxies are significantly different from each other. We infer that VCC 1287 has an old (≳7.7 Gyr) and surprisingly metal-poor ([Z/Z⊙] ≾ −1.0) stellar population, even after marginalizing over uncertainties on diffuse interstellar dust. In contrast, the field UDG DGSAT I shows evidence of being younger than the Virgo UDG, with an extended star formation history and an age posterior extending down to ~3 Gyr. The stellar metallicity of DGSAT I is sub-solar but higher than that of the Virgo UDG, with [Z/Z⊙] = -0.63^(+0.35)_(-0.62); in the case of exactly zero diffuse interstellar dust, DGSAT I may even have solar metallicity. With VCC 1287 and several Coma UDGs, a general picture is emerging where cluster UDGs may be "failed" galaxies, but the field UDG DGSAT I seems more consistent with a stellar feedback-induced expansion scenario. In the future, our approach can be applied to a large and diverse sample of UDGs down to faint surface brightness limits, with the goal of constraining their stellar ages, stellar metallicities, and circumstellar and diffuse interstellar dust content.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Pandya, Viraj0000-0002-2499-9205
Romanowsky, Aaron J.0000-0003-2473-0369
Laine, Seppo0000-0003-1250-8314
Brodie, Jean P.0000-0002-9658-8763
Villaume, Alexa0000-0003-1887-0621
Martín-Navarro, Ignacio0000-0003-4266-5580
Martínez-Delgado, David0000-0003-3835-2231
van Dokkum, Pieter0000-0002-8282-9888
Additional Information:© 2018 The American Astronomical Society. Received 2017 November 7; revised 2018 February 12; accepted 2018 March 4; published 2018 April 30. We greatly thank Laura Ferrarese for providing us with Elixir-LSB CFHT imaging of VCC 1287. We thank James Ingalls for his help with "de-striping" our IRAC images, and Sean Carey and Tom Jarrett for advice on systematic uncertainties in IRAC imaging. We thank Fangzhou Jiang, Avishai Dekel, Andi Burkert, and Soeren Larsen for useful discussions; Johnny Greco and Chris Conselice for helpful comments on the paper; and the anonymous referee for invaluable suggestions. V.P. acknowledges useful conversations with Arianna di Cintio, Meng Gu, Timothy Carleton, and Tsang Keung Chan at the 2017 Santa Cruz Galaxy Formation Workshop, and separately Rachel Somerville, Joel Primack, Sandy Faber, and David Koo. A.J.R. was supported by National Science Foundation grant AST-1616710 and as a Research Corporation for Science Advancement Cottrell Scholar. J.P.B. was supported by NSF AST-1616598. This research was supported in part by the National Science Foundation under grant NSF PHY11-25915. This work is based in part on observations made with and archival data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This research made use of Astropy (particularly photutils), a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Cottrell Scholar of Research CorporationUNSPECIFIED
Subject Keywords:galaxies: clusters: general – galaxies: dwarf – galaxies: evolution – galaxies: formation – galaxies: photometry – galaxies: stellar content
Issue or Number:1
Record Number:CaltechAUTHORS:20180430-102939714
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Official Citation:Viraj Pandya et al 2018 ApJ 858 29
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86125
Deposited By: Tony Diaz
Deposited On:30 Apr 2018 17:38
Last Modified:15 Nov 2021 20:35

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