Minor Mergers Are Not Enough: The Importance of Major Mergers during Brightest Cluster Galaxy Assembly
We investigate the roles of major and minor mergers during brightest cluster galaxy (BCG) assembly using surface brightness profiles, line indices, and fundamental plane relations. Based on our own sample and consistently reanalyzed Sloan Digital Sky Survey data, we find that BCGs and luminous norma...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal Supplement Series |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4365/ace052 |
| _version_ | 1797698079316508672 |
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| author | Matthias Kluge Ralf Bender |
| author_facet | Matthias Kluge Ralf Bender |
| author_sort | Matthias Kluge |
| collection | DOAJ |
| description | We investigate the roles of major and minor mergers during brightest cluster galaxy (BCG) assembly using surface brightness profiles, line indices, and fundamental plane relations. Based on our own sample and consistently reanalyzed Sloan Digital Sky Survey data, we find that BCGs and luminous normal ellipticals (LNEs) have similar central velocity dispersions, central absorption line strengths, and central surface brightnesses. However, BCGs are more luminous due to their much larger radial extent. These properties result in a flattening of the Faber–Jackson and Mg _b –luminosity relations above 10 ^10.6 ${L}_{\odot ,g^{\prime} }$ . We use this effect to estimate an amount of 60%–80% of accreted and merged light in BCGs relative to LNEs, which agrees with results from cosmological simulations. We determine the contribution of this excess light (EL) at each radius from the difference between the surface flux profiles of BCGs and LNEs. It is small in the center but increases steeply to 50% at ∼3 kpc radius. The shape of these profiles suggests that BCGs could be formed from LNEs in three major merger processes. This is also consistent with the mild increase of the Sérsic indices from n ≈ 4 to n ≈ 6, as confirmed in merger simulations. We note that minor mergers cannot be the dominant origin of the BCG’s EL because they deposit too few stars at intermediate radii r ≲ 20 kpc. The shape of the EL profile also explains a detected offset of 0.14 dex of the fundamental planes for BCGs and LNEs relative to each other. |
| first_indexed | 2024-03-12T03:49:04Z |
| format | Article |
| id | doaj.art-0746f778f815494c9675d59bf12b7586 |
| institution | Directory Open Access Journal |
| issn | 0067-0049 |
| language | English |
| last_indexed | 2024-03-12T03:49:04Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Supplement Series |
| spelling | doaj.art-0746f778f815494c9675d59bf12b75862023-09-03T12:30:36ZengIOP PublishingThe Astrophysical Journal Supplement Series0067-00492023-01-0126724110.3847/1538-4365/ace052Minor Mergers Are Not Enough: The Importance of Major Mergers during Brightest Cluster Galaxy AssemblyMatthias Kluge0https://orcid.org/0000-0002-9618-2552Ralf Bender1https://orcid.org/0000-0001-7179-0626University-Observatory, Ludwig-Maximilians-University , Scheinerstrasse 1, D-81679 Munich, Germany ; mkluge@mpe.mpg.de; Max Planck Institute for Extraterrestrial Physics , Giessenbachstrasse, D-85748 Garching, GermanyUniversity-Observatory, Ludwig-Maximilians-University , Scheinerstrasse 1, D-81679 Munich, Germany ; mkluge@mpe.mpg.de; Max Planck Institute for Extraterrestrial Physics , Giessenbachstrasse, D-85748 Garching, GermanyWe investigate the roles of major and minor mergers during brightest cluster galaxy (BCG) assembly using surface brightness profiles, line indices, and fundamental plane relations. Based on our own sample and consistently reanalyzed Sloan Digital Sky Survey data, we find that BCGs and luminous normal ellipticals (LNEs) have similar central velocity dispersions, central absorption line strengths, and central surface brightnesses. However, BCGs are more luminous due to their much larger radial extent. These properties result in a flattening of the Faber–Jackson and Mg _b –luminosity relations above 10 ^10.6 ${L}_{\odot ,g^{\prime} }$ . We use this effect to estimate an amount of 60%–80% of accreted and merged light in BCGs relative to LNEs, which agrees with results from cosmological simulations. We determine the contribution of this excess light (EL) at each radius from the difference between the surface flux profiles of BCGs and LNEs. It is small in the center but increases steeply to 50% at ∼3 kpc radius. The shape of these profiles suggests that BCGs could be formed from LNEs in three major merger processes. This is also consistent with the mild increase of the Sérsic indices from n ≈ 4 to n ≈ 6, as confirmed in merger simulations. We note that minor mergers cannot be the dominant origin of the BCG’s EL because they deposit too few stars at intermediate radii r ≲ 20 kpc. The shape of the EL profile also explains a detected offset of 0.14 dex of the fundamental planes for BCGs and LNEs relative to each other.https://doi.org/10.3847/1538-4365/ace052Galaxy formationScaling relationsElliptical galaxiesGalaxy photometryGalaxy spectroscopy |
| spellingShingle | Matthias Kluge Ralf Bender Minor Mergers Are Not Enough: The Importance of Major Mergers during Brightest Cluster Galaxy Assembly The Astrophysical Journal Supplement Series Galaxy formation Scaling relations Elliptical galaxies Galaxy photometry Galaxy spectroscopy |
| title | Minor Mergers Are Not Enough: The Importance of Major Mergers during Brightest Cluster Galaxy Assembly |
| title_full | Minor Mergers Are Not Enough: The Importance of Major Mergers during Brightest Cluster Galaxy Assembly |
| title_fullStr | Minor Mergers Are Not Enough: The Importance of Major Mergers during Brightest Cluster Galaxy Assembly |
| title_full_unstemmed | Minor Mergers Are Not Enough: The Importance of Major Mergers during Brightest Cluster Galaxy Assembly |
| title_short | Minor Mergers Are Not Enough: The Importance of Major Mergers during Brightest Cluster Galaxy Assembly |
| title_sort | minor mergers are not enough the importance of major mergers during brightest cluster galaxy assembly |
| topic | Galaxy formation Scaling relations Elliptical galaxies Galaxy photometry Galaxy spectroscopy |
| url | https://doi.org/10.3847/1538-4365/ace052 |
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