Cover Page
The handle http://hdl.handle.net/1887/66824 holds various files of this Leiden University
dissertation.
Author: Barber, C.R.
Title: Monsters in the deep: using simulations to understand the excess baryonic mass in
the centres of high-mass, early-type galaxies
Monsters in the Deep
Using simulations to understand the excess baryonic mass
in the centres of high-mass, early-type galaxies
Proefschrift
ter verkrijging van
de graad van Doctor aan de Universiteit Leiden, op gezag van Rector Magnificus prof. mr. C.J.J.M. Stolker,
volgens besluit van het College voor Promoties te verdedigen op dinsdag 20 November 2018
klokke 10.00 uur
door
Christopher Ryan Barber
Promotor: Prof. dr. Joop Schaye
Co-promotor: Dr. Robert A. Crain (Liverpool John Moores University, UK) Promotiecommissie: Prof. dr. Huub Röttgering
Prof. dr. Marijn Franx
Prof. dr. Charlie Conroy (Harvard University, USA) Dr. Madusha Gunawardhana
Dr. Russell Smith (Durham University, UK)
An electronic version of this thesis can be found at openaccess.leidenuniv.nl
Cover designed and created by Kyle Barber
“If you wish to make an apple pie from scratch,
you must first invent the Universe.”
– Carl Sagan
1Contents v
Contents
1 Introduction 1
1.1 Galaxy formation and evolution . . . 2
1.2 Black hole monsters . . . 3
1.3 Stellar population monsters . . . 6
1.4 Simulations of galaxy formation and evolution . . . 9
1.5 This thesis . . . 11
1.6 Outlook . . . 13
2 The origin of compact galaxies with anomalously high black hole masses 15 2.1 Introduction . . . 16
2.2 The EAGLE Simulations . . . 18
2.2.1 Subgrid physics . . . 18
2.2.2 Subhalo identification and corrections . . . 20
2.3 Outliers in the MBH− M?relation . . . 21
2.4 The origin of outliers from the MBH− M?relation . . . 25
2.4.1 Environment at z = 0 . . . . 27
2.4.2 Evolution . . . 28
2.4.3 Tidal stripping as the primary cause of anomalously high MBH(M?) 29 2.4.4 Early formation time as a secondary cause of anomalously high MBH(M?) . . . 32
2.4.5 The relative importance of tidal stripping and early formation . 35 2.4.6 Galaxies with “monstrous” black holes in galaxy cluster environments . . . 38
2.5 Relation to compact galaxies . . . 42
2.6 Summary and Conclusions . . . 46
3 Calibrated, cosmological, hydrodynamical simulations with variable IMFs I: Method and effect on global galaxy scaling relations 49 3.1 Introduction . . . 50
3.2 Methods . . . 53
3.2.1 The EAGLE simulations . . . 54
3.2.2 IMF calibration . . . 55
vi Contents
3.3.1 IMF vs stellar velocity dispersion . . . 65
3.3.2 Subgrid calibration diagnostics . . . 71
3.4 Effect of variable IMFs on galaxy properties . . . 76
3.4.1 Alpha enhancement . . . 76
3.4.2 Metallicities . . . 77
3.4.3 Star formation . . . 81
3.4.4 ETG galaxy sizes . . . 84
3.5 Summary and Conclusions . . . 86
3.A Aperture effects and IMF calibration details . . . 89
3.B Self-consistency tests . . . 91
3.C The dwarf-to-giant ratio . . . 94
4 Calibrated, cosmological, hydrodynamical simulations with variable IMFs II: Correlations between the IMF and global galaxy properties 99 4.1 Introduction . . . 100
4.2 Simulations . . . 101
4.3 Is the (M/L)-excess a good tracer of the IMF? . . . 105
4.4 Trends between the (M/L)-excess and global galactic properties . . . . 107
4.4.1 MLE vs age . . . 107
4.4.2 MLE vs metallicity . . . 111
4.4.3 MLE vs [Mg/Fe] . . . 112
4.4.4 MLE vs Chabrier-inferred galaxy mass, luminosity, and size . . . 113
4.4.5 MLE vs MBH/M? . . . 116
4.4.6 Which observables correlate most strongly with the MLE? . . . . 118
4.5 MLE of satellite galaxies . . . 120
4.6 Summary and Conclusions . . . 121
5 Calibrated, cosmological, hydrodynamical simulations with variable IMFs III: Spatially-resolved properties and evolution 125 5.1 Introduction . . . 126
5.2 Simulations . . . 128
5.3 IMF trends within galaxies . . . 131
5.3.1 Sample selection . . . 131
5.3.2 Radial IMF gradients . . . 134
5.3.3 Radial gradients in stellar population properties . . . 143
5.3.4 IMF vs local quantities . . . 145
5.4 Redshift dependence of galaxy properties . . . 148
5.4.1 Redshift dependence of the IMF . . . 148
5.4.2 Redshift-dependent cosmic properties . . . 155
5.5 Discussion . . . 157
5.6 Summary and Conclusions . . . 159
Contents vii
Nederlandse Samenvatting 171
Publications 175
Curriculum Vitae 177
