Stellar populations and merger rates of brightest cluster galaxies a billion years ago: SDSS MaNGA IFU spectroscopy

Journal Article · 19 April 2024 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stae1055 · OSTI ID:2345967

Edwards, Louise O. V. ; Hamel, Kevin A. S. J.; Shy, Joseph C.; Hernandez, Jonathan; Holguin Luna, Priscilla; Higgins, Denvir J.; Chawla, Theo; Gavidia, Adriana; Cole, Samuel

ABSTRACT We investigate the spectroscopic properties of 85 brightest cluster galaxies (BCGs) and their companions observed with the SDSS MaNGA integral field unit. Galaxy redshifts are between 0.08 < z < 0.15, allowing for a field-of-view up to 80 × 80 kpc. For the main galaxies: the average age of the BCG cores is 7.66$$\, \pm \,$$1.36 Gyr with no significant gradient out to $$2\, R_ {e}$$; the average metallicity of the BCG cores is $$[Z/H]=0.23\, \pm \, 0.03$$ with a negative gradient of Δ[Z/H]/Δ(R/Re)  = –0.14$$\, \pm \, 0.09$$ which flattens beyond $$1.2\, R_ {e}$$. Velocity dispersion gradients are mostly flat, but a few positive slopes are seen in the most massive galaxies. Emission lines are present in 12 of the BCGs, most often confined to the central $$\sim 2\,$$ kpc with emission line ratios well-described by a LINER or AGN excitation source. There are 78 companion galaxies identified and 9 have nebular emission lines that indicate recent star formation. The companions with flux ratios of 4:1 and 20:1 within 30 kpc of their BCG’s core are studied. The companion galaxies have a median age of 7.65$$\, \pm \,$$1.55 Gyr and are high-metallicity systems, with a median [Z/H] = 0.17  ±  0.07. Close spectroscopic companions with higher merging probabilities have an average merging time of 0.5 ± 0.2 Gyr. The average merger rate is 0.08$$\, \pm \, 0.12 \,$$ Gyr−1 for 4:1 companions and 0.26$$\, \pm \, 0.22 \,$$ Gyr−1 for 20:1 companions, allowing for an increase in mass of 2.3$$\, \pm \,$$3.4 per cent Gyr−1 and 3.5$$\, \pm \,$$3.2 per cent Gyr−1, respectively.

• Sponsoring Organization: USDOE
• OSTI ID: 2345967
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 4 Vol. 530; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United Kingdom
• Language: English