Low Metallicities and Old Ages for Three Ultra-diffuse Galaxies in the Coma Cluster

Meng Gu; Charlie Conroy; David Law; Pieter Van Dokkum; Renbin Yan; David Wake; Kevin Bundy; Allison Merritt; Roberto Abraham; Jielai Zhang; Matthew Bershady; Dmitry Bizyaev; Jonathan Brinkmann; Niv Drory; Kathleen Grabowski; Karen Masters; Kaike Pan; John Parejko; Anne Marie Weijmans; Kai Zhang

doi:10.3847/1538-4357/aabbae

Low Metallicities and Old Ages for Three Ultra-diffuse Galaxies in the Coma Cluster

Meng Gu, Charlie Conroy, David Law, Pieter Van Dokkum, Renbin Yan, David Wake, Kevin Bundy, Allison Merritt, Roberto Abraham, Jielai Zhang, Matthew Bershady, Dmitry Bizyaev, Jonathan Brinkmann, Niv Drory, Kathleen Grabowski, Karen Masters, Kaike Pan, John Parejko, Anne Marie Weijmans, Kai Zhang

Physics And Astronomy

Research output: Contribution to journal › Article › peer-review

51 Scopus citations

Abstract

A large population of ultra-diffuse galaxies (UDGs) was recently discovered in the Coma cluster. Here we present optical spectra of three such UDGs, DF 7, DF 44, and DF 17, which have central surface brightnesses of μ _g ≈24.4-25.1 mag arcsec^-2. The spectra were acquired as part of an ancillary program within the SDSS-IV MaNGA Survey. We stacked 19 fibers in the central regions from larger integral field units (IFUs) per source. With over 13.5 hr of on-source integration, we achieved a mean signal-to-noise ratio in the optical of 9.5 ∗^-1, 7.9 ∗^-1, and 5.0 ∗^-1, respectively, for DF 7, DF 44, and DF 17. Stellar population models applied to these spectra enable measurements of recession velocities, ages, and metallicities. The recession velocities of DF 7, DF 44, and DF 17 are km s^-1, km s^-1, and km s^-1, spectroscopically confirming that all of them reside in the Coma cluster. The stellar populations of these three galaxies are old and metal-poor, with ages of Gyr, Gyr, and Gyr, and iron abundances of [Fe/H] , , and , respectively. Their stellar masses are (3-6) ×10⁸ M _o. The UDGs in our sample are as old or older than galaxies at similar stellar mass or velocity dispersion (only DF 44 has an independently measured dispersion). They all follow the well-established stellar mass-stellar metallicity relation, while DF 44 lies below the velocity dispersion-metallicity relation. These results, combined with the fact that UDGs are unusually large for their stellar masses, suggest that stellar mass plays a more important role in setting stellar population properties for these galaxies than either size or surface brightness.

Original language	English
Article number	37
Journal	Astrophysical Journal
Volume	859
Issue number	1
DOIs	https://doi.org/10.3847/1538-4357/aabbae
State	Published - May 20 2018

Bibliographical note

Funding Information:
We thank the referee for helpful comments that improved this paper. M.G. acknowledges support from the National Science Foundation Graduate Research Fellowship. C.C. acknowledges support from NASA grant NNX15AK14G, NSF grant AST-1313280, and the Packard Foundation. M.B. acknowledges funding from NSF/AST-1517006. A.W. acknowledges support of a Leverhulme Trust Early Career Fellowship. The computations in this paper were run on the Odyssey cluster supported by the FAS Division of Science, Research Computing Group at Harvard University.

Funding Information:
Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS website ishttp://www.sdss.org.

Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved.

Keywords

galaxies: clusters: individual (Coma)
galaxies: evolution
galaxies: stellar content

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.3847/1538-4357/aabbae

Cite this

Gu, M., Conroy, C., Law, D., Dokkum, P. V., Yan, R., Wake, D., Bundy, K., Merritt, A., Abraham, R., Zhang, J., Bershady, M., Bizyaev, D., Brinkmann, J., Drory, N., Grabowski, K., Masters, K., Pan, K., Parejko, J., Weijmans, A. M., & Zhang, K. (2018). Low Metallicities and Old Ages for Three Ultra-diffuse Galaxies in the Coma Cluster. Astrophysical Journal, 859(1), Article 37. https://doi.org/10.3847/1538-4357/aabbae

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title = "Low Metallicities and Old Ages for Three Ultra-diffuse Galaxies in the Coma Cluster",

abstract = "A large population of ultra-diffuse galaxies (UDGs) was recently discovered in the Coma cluster. Here we present optical spectra of three such UDGs, DF 7, DF 44, and DF 17, which have central surface brightnesses of μ g ≈24.4-25.1 mag arcsec-2. The spectra were acquired as part of an ancillary program within the SDSS-IV MaNGA Survey. We stacked 19 fibers in the central regions from larger integral field units (IFUs) per source. With over 13.5 hr of on-source integration, we achieved a mean signal-to-noise ratio in the optical of 9.5 ∗-1, 7.9 ∗-1, and 5.0 ∗-1, respectively, for DF 7, DF 44, and DF 17. Stellar population models applied to these spectra enable measurements of recession velocities, ages, and metallicities. The recession velocities of DF 7, DF 44, and DF 17 are km s-1, km s-1, and km s-1, spectroscopically confirming that all of them reside in the Coma cluster. The stellar populations of these three galaxies are old and metal-poor, with ages of Gyr, Gyr, and Gyr, and iron abundances of [Fe/H] , , and , respectively. Their stellar masses are (3-6) ×108 M o. The UDGs in our sample are as old or older than galaxies at similar stellar mass or velocity dispersion (only DF 44 has an independently measured dispersion). They all follow the well-established stellar mass-stellar metallicity relation, while DF 44 lies below the velocity dispersion-metallicity relation. These results, combined with the fact that UDGs are unusually large for their stellar masses, suggest that stellar mass plays a more important role in setting stellar population properties for these galaxies than either size or surface brightness.",

keywords = "galaxies: clusters: individual (Coma), galaxies: evolution, galaxies: stellar content",

author = "Meng Gu and Charlie Conroy and David Law and Dokkum, {Pieter Van} and Renbin Yan and David Wake and Kevin Bundy and Allison Merritt and Roberto Abraham and Jielai Zhang and Matthew Bershady and Dmitry Bizyaev and Jonathan Brinkmann and Niv Drory and Kathleen Grabowski and Karen Masters and Kaike Pan and John Parejko and Weijmans, {Anne Marie} and Kai Zhang",

note = "Funding Information: We thank the referee for helpful comments that improved this paper. M.G. acknowledges support from the National Science Foundation Graduate Research Fellowship. C.C. acknowledges support from NASA grant NNX15AK14G, NSF grant AST-1313280, and the Packard Foundation. M.B. acknowledges funding from NSF/AST-1517006. A.W. acknowledges support of a Leverhulme Trust Early Career Fellowship. The computations in this paper were run on the Odyssey cluster supported by the FAS Division of Science, Research Computing Group at Harvard University. Funding Information: Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS website ishttp://www.sdss.org. Publisher Copyright: {\textcopyright} 2018. The American Astronomical Society. All rights reserved.",

year = "2018",

month = may,

day = "20",

doi = "10.3847/1538-4357/aabbae",

language = "English",

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Gu, M, Conroy, C, Law, D, Dokkum, PV, Yan, R, Wake, D, Bundy, K, Merritt, A, Abraham, R, Zhang, J, Bershady, M, Bizyaev, D, Brinkmann, J, Drory, N, Grabowski, K, Masters, K, Pan, K, Parejko, J, Weijmans, AM & Zhang, K 2018, 'Low Metallicities and Old Ages for Three Ultra-diffuse Galaxies in the Coma Cluster', Astrophysical Journal, vol. 859, no. 1, 37. https://doi.org/10.3847/1538-4357/aabbae

TY - JOUR

T1 - Low Metallicities and Old Ages for Three Ultra-diffuse Galaxies in the Coma Cluster

AU - Gu, Meng

AU - Conroy, Charlie

AU - Law, David

AU - Dokkum, Pieter Van

AU - Yan, Renbin

AU - Wake, David

AU - Bundy, Kevin

AU - Merritt, Allison

AU - Abraham, Roberto

AU - Zhang, Jielai

AU - Bershady, Matthew

AU - Bizyaev, Dmitry

AU - Brinkmann, Jonathan

AU - Drory, Niv

AU - Grabowski, Kathleen

AU - Masters, Karen

AU - Pan, Kaike

AU - Parejko, John

AU - Weijmans, Anne Marie

AU - Zhang, Kai

N1 - Funding Information: We thank the referee for helpful comments that improved this paper. M.G. acknowledges support from the National Science Foundation Graduate Research Fellowship. C.C. acknowledges support from NASA grant NNX15AK14G, NSF grant AST-1313280, and the Packard Foundation. M.B. acknowledges funding from NSF/AST-1517006. A.W. acknowledges support of a Leverhulme Trust Early Career Fellowship. The computations in this paper were run on the Odyssey cluster supported by the FAS Division of Science, Research Computing Group at Harvard University. Funding Information: Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS website ishttp://www.sdss.org. Publisher Copyright: © 2018. The American Astronomical Society. All rights reserved.

PY - 2018/5/20

Y1 - 2018/5/20

N2 - A large population of ultra-diffuse galaxies (UDGs) was recently discovered in the Coma cluster. Here we present optical spectra of three such UDGs, DF 7, DF 44, and DF 17, which have central surface brightnesses of μ g ≈24.4-25.1 mag arcsec-2. The spectra were acquired as part of an ancillary program within the SDSS-IV MaNGA Survey. We stacked 19 fibers in the central regions from larger integral field units (IFUs) per source. With over 13.5 hr of on-source integration, we achieved a mean signal-to-noise ratio in the optical of 9.5 ∗-1, 7.9 ∗-1, and 5.0 ∗-1, respectively, for DF 7, DF 44, and DF 17. Stellar population models applied to these spectra enable measurements of recession velocities, ages, and metallicities. The recession velocities of DF 7, DF 44, and DF 17 are km s-1, km s-1, and km s-1, spectroscopically confirming that all of them reside in the Coma cluster. The stellar populations of these three galaxies are old and metal-poor, with ages of Gyr, Gyr, and Gyr, and iron abundances of [Fe/H] , , and , respectively. Their stellar masses are (3-6) ×108 M o. The UDGs in our sample are as old or older than galaxies at similar stellar mass or velocity dispersion (only DF 44 has an independently measured dispersion). They all follow the well-established stellar mass-stellar metallicity relation, while DF 44 lies below the velocity dispersion-metallicity relation. These results, combined with the fact that UDGs are unusually large for their stellar masses, suggest that stellar mass plays a more important role in setting stellar population properties for these galaxies than either size or surface brightness.

AB - A large population of ultra-diffuse galaxies (UDGs) was recently discovered in the Coma cluster. Here we present optical spectra of three such UDGs, DF 7, DF 44, and DF 17, which have central surface brightnesses of μ g ≈24.4-25.1 mag arcsec-2. The spectra were acquired as part of an ancillary program within the SDSS-IV MaNGA Survey. We stacked 19 fibers in the central regions from larger integral field units (IFUs) per source. With over 13.5 hr of on-source integration, we achieved a mean signal-to-noise ratio in the optical of 9.5 ∗-1, 7.9 ∗-1, and 5.0 ∗-1, respectively, for DF 7, DF 44, and DF 17. Stellar population models applied to these spectra enable measurements of recession velocities, ages, and metallicities. The recession velocities of DF 7, DF 44, and DF 17 are km s-1, km s-1, and km s-1, spectroscopically confirming that all of them reside in the Coma cluster. The stellar populations of these three galaxies are old and metal-poor, with ages of Gyr, Gyr, and Gyr, and iron abundances of [Fe/H] , , and , respectively. Their stellar masses are (3-6) ×108 M o. The UDGs in our sample are as old or older than galaxies at similar stellar mass or velocity dispersion (only DF 44 has an independently measured dispersion). They all follow the well-established stellar mass-stellar metallicity relation, while DF 44 lies below the velocity dispersion-metallicity relation. These results, combined with the fact that UDGs are unusually large for their stellar masses, suggest that stellar mass plays a more important role in setting stellar population properties for these galaxies than either size or surface brightness.

KW - galaxies: clusters: individual (Coma)

KW - galaxies: evolution

KW - galaxies: stellar content

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U2 - 10.3847/1538-4357/aabbae

DO - 10.3847/1538-4357/aabbae

M3 - Article

AN - SCOPUS:85048014782

SN - 0004-637X

VL - 859

JO - Astrophysical Journal

JF - Astrophysical Journal

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M1 - 37

ER -

Low Metallicities and Old Ages for Three Ultra-diffuse Galaxies in the Coma Cluster

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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