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The VLT-MUSE and ALMA view of the MACS 1931.8-2635 brightest cluster galaxy

Ciocan, B. I. and Ziegler, B. L. and Verdugo, M. and Papaderos, P. and Fogarty, K. and Donahue, M. and Postman, M. (2021) The VLT-MUSE and ALMA view of the MACS 1931.8-2635 brightest cluster galaxy. Astronomy and Astrophysics, 649 . Art. No. A23. ISSN 0004-6361. doi:10.1051/0004-6361/202040010.

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We reveal the importance of ongoing in situ star formation in the brightest cluster galaxy (BCG) in the massive cool-core CLASH cluster MACS 1931.8-2635 at a redshift of z = 0.35 by analysing archival VLT-MUSE optical integral field spectroscopy. Using a multi-wavelength approach, we assessed the stellar and warm ionised medium components, which were spatially resolved by the VLT-MUSE spectroscopy, and linked them to the molecular gas by incorporating sub-mm ALMA observations. We measured the fluxes of strong emission lines such as: [O II] λ3727, Hβ, [O III] λ5007, Hα, [N II] λ 6584, and [S II] λ6718, 6732, which allowed us to determine the physical conditions of the warm ionised gas, such as electron temperature, electron density, extinction, ionisation parameter, (O/H) gas metallicities, star formation rates, and gas kinematics, as well as the star formation history of the system. Our analysis reveals the ionising sources in different regions of the galaxy. The ionised gas flux brightness peak corresponds to the location of the supermassive black hole in the BCG and the system shows a diffuse warm ionised gas tail extending 30 kpc in the north-east direction. The ionised and molecular gas are co-spatial and co-moving, with the gaseous component in the tail likely falling inward, providing fuel for star formation and accretion-powered nuclear activity. The gas is ionised by a mix of star formation and other energetic processes which give rise to LINER-like emission, with active galactic nuclei emission dominant only in the BCG core. We measured a star formation rate of ∼97 M⊙ yr⁻¹, with its peak at the BCG core. However, star formation accounts for only 50–60% of the energetics needed to ionise the warm gas. The stellar mass growth of the BCG at z < 0.5 is dominated either by in situ star formation generated by thermally unstable intracluster medium cooling or by dry mergers, with these mechanisms accounting for the build-up of 20% of the stellar mass of the system. Our measurements reveal that the most central regions of the BCG contain the lowest gas-phase oxygen abundance, whereas the Hα arm exhibits slightly more elevated values, suggesting the transport of gas out to large distances from the centre as a result of active galactic nuclei outbursts. The galaxy is a dispersion-dominated system that is typical for massive, elliptical galaxies. The gas and stellar kinematics are decoupled, with the gaseous velocity fields being more closely related to the bulk motions of the intracluster medium.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemCode
Fogarty, K.0000-0002-2691-2476
Donahue, M.0000-0002-2808-0853
Postman, M.0000-0002-9365-7989
Additional Information:© ESO 2021. Article published by EDP Sciences. Received 27 November 2020; Accepted 26 January 2021; Published online 05 May 2021. We would like to express our deep gratitude to the members of the observational extragalactic astrophysics group from the department of astrophysics, University of Vienna. Special thanks to Christian Maier and Asmus Böhm for all the valuable discussions and pieces of advice! We would also like to express our gratitude to Maria Luísa Gomes Buzzo for all her help related to analysis of the MUSE data. We would especially like to thank the anonymous referee for providing constructive comments and help in improving the manuscript. This work was supported through FCT grants UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020 and the project “Identifying the Earliest Supermassive Black Holes with ALMA (IdEaS with ALMA)” (PTDC/FIS-AST/29245/2017). This research made use of the following PYTHON packages: Astropy (Astropy Collaboration 2013), numpy (van der Walt et al. 2011), matplotlib (Hunter 2007), MPDAF (Bacon et al. 2016), CMasher (van der Velden 2020).
Funding AgencyGrant Number
Fundação para a Ciência e a Tecnologia (FCT)UID/FIS/04434/2019
Fundação para a Ciência e a Tecnologia (FCT)UIDB/04434/2020
Fundação para a Ciência e a Tecnologia (FCT)UIDP/04434/2020
Fundação para a Ciência e a Tecnologia (FCT)PTDC/FIS-AST/29245/2017
Subject Keywords:Galaxy: evolution – Galaxy: kinematics and dynamics – Galaxy: fundamental parameters
Record Number:CaltechAUTHORS:20210513-093210997
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Official Citation:The VLT-MUSE and ALMA view of the MACS 1931.8-2635 brightest cluster galaxy. B. I. Ciocan, B. L. Ziegler, M. Verdugo, P. Papaderos, K. Fogarty, M. Donahue and M. Postman. A&A, 649 (2021) A23; DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109109
Deposited By: Tony Diaz
Deposited On:13 May 2021 16:43
Last Modified:13 May 2021 16:43

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