Clocking the formation of today’s largest galaxies: wide field integral spectroscopy of brightest cluster galaxies and their surroundings

Journal Article · 27 September 2019 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stz2706 · OSTI ID:1577002

Edwards, Louise O. V. ^[1]; Salinas, Matthew ^[1]; Stanley, Steffanie ^[1]; Holguin West, Priscilla E. ^[1]; Trierweiler, Isabella ^[2]; Alpert, Hannah ^[3]; Coelho, Paula ^[4]; Koppaka, Saisneha ^[5]; Tremblay, Grant R. ^[6]; Martel, Hugo ^[7]; Li, Yuan ^[8]

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1. Department of Physics, Cal Poly State University, San Luis Obispo, CA 93407, USA
2. Department of Physics and Astronomy, Yale University, New Haven, CT 06520, USA, Division of Astronomy and Astrophysics, University of California Los Angeles, Los Angeles, CA 90095, USA
3. Department of Physics and Astronomy, Yale University, New Haven, CT 06520, USA, Aeronautics and Astronautics Department, Stanford University, Stanford, CA 94305, USA
4. Departamento de Astronomia, Universidade de São Paulo, IAG, São Paulo, 05508-909, Brazil
5. Department of Physics and Astronomy, Yale University, New Haven, CT 06520, USA
6. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
7. Département de physique, de génie physique et d’optique, Université Laval, Québec, QC, G1V 0A6, Canada, Centre de Recherche en Astrophysique du Québec, C. P. 6128, Succ. Centre-Ville, Montéal, QC, H3C 3J7Q, Canada
8. Center for Computational Astronomy (CCA), Flatiron Institute, New York, NY 10010, USA

ABSTRACT The formation and evolution of local brightest cluster galaxies (BCGs) is investigated by determining the stellar populations and dynamics from the galaxy core, through the outskirts and into the intracluster light (ICL). Integral spectroscopy of 23 BCGs observed out to $$4\, r_{e}$$ is collected and high signal-to-noise regions are identified. Stellar population synthesis codes are used to determine the age, metallicity, velocity, and velocity dispersion of stars within each region. The ICL spectra are best modelled with populations that are younger and less metal-rich than those of the BCG cores. The average BCG core age of the sample is $$\rm 13.3\pm 2.8\, Gyr$$ and the average metallicity is $$\rm [Fe/H] = 0.30\pm 0.09$$, whereas for the ICL the average age is $$\rm 9.2\pm 3.5\, Gyr$$ and the average metallicity is $$\rm [Fe/H] = 0.18\pm 0.16$$. The velocity dispersion profile is seen to be rising or flat in most of the sample (17/23), and those with rising values reach the value of the host cluster’s velocity dispersion in several cases. The most extended BCGs are closest to the peak of the cluster’s X-ray luminosity. The results are consistent with the idea that the BCG cores and inner regions formed quickly and long ago, with the outer regions and ICL forming more recently, and continuing to assemble through minor merging. Any recent star formation in the BCGs is a minor component, and is associated with the cluster cool core status.

• Sponsoring Organization: USDOE
• OSTI ID: 1577002
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 2 Vol. 491; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United Kingdom
• Language: English