University of Groningen
Gravitational lensing at milliarcsecond angular resolution
Spingola, Cristiana
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2019
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Spingola, C. (2019). Gravitational lensing at milliarcsecond angular resolution. Rijksuniversiteit Groningen.
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Gravitational lensing
at milliarcsecond angular resolution
Proefschrift
ter verkrijging van de graad van doctor aan de
Rijksuniversiteit Groningen
op gezag van de
rector magnificus prof. dr. E. Sterken
en volgens besluit van het College voor Promoties.
De openbare verdediging zal plaatsvinden op
maandag 4 februari 2019 om 12:45 uur
door
Cristiana Spingola
geboren op 25 januari 1989
te Perugia, Italië
Promotores Prof. dr. J. P. McKean Prof. dr. L. V. E. Koopmans Beoordelingscommissie Prof. dr. P. D. Barthel Prof. dr. S. Serjeant Prof. dr. R. L. Webster
Front cover: The contours indicate the gravitationally lensed radio emission on milliarcsecond scales from AGN jets at z = 3.2 in the lensing system MG J0751+2716. Back cover: The contours represent the intrinsic radio emission of the AGN jets at z = 3.2 in the lensing system MG J0751+2716. The background consists of paint drops on black (from Freepik).
ISBN: 978-94-034-1286-3 (electronic version) ISBN: 978-94-034-1285-6 (printed version)
To Davide, I couldn’t make this without you.
Contents
1 Scientific Introduction 9
1.1 Challenges to the ΛCDM model 9
1.2 The Universe under a cosmic telescope 12
1.2.1 Basic concepts of gravitational lensing 12
1.2.2 Gravitational lens modelling 16
1.2.3 Deviations from a smooth model 18
1.3 Gravitational lensing at radio wavelengths 19
1.3.1 High angular resolution with interferometry 21
1.3.2 Radio interferometers used in this thesis 22
1.4 Thesis outline 26
2 Modelling gravitationally lensed radio arcs
imaged with global VLBI observations 29
2.1 Introduction 30
2.2 Observations 34
2.2.1 Very Long Baseline Interferometry data 34
2.2.2 Hubble Space Telescope data 36
2.3 Lens Modelling 38
2.3.1 Parametric lens modelling 38
2.3.2 Results 43
2.4 Discussion 47
2.4.1 Precision lens modelling with global VLBI
observations 47
2.4.2 Evidence for additional mass structure 50
2.4.3 Evidence in favour of the two-phase galaxy
formation scenario 51
2.5 Summary and Conclusions 52
3 Resolving the CO (1–0) molecular gas around
two radio-loud dust-obscured lensed AGN at
high redshift 57 3.1 Introduction 58 3.2 Targets 61 3.2.1 MG J0751+2716 61 3.2.2 JVAS B1938+666 62 3.3 Observations 62
3.3.1 W. M. Keck Telescope adaptive optics 65
3.3.2 Hubble Space Telescope 65
3.3.3 Karl G. Jansky Very Large Array 67
3.4 Lens plane properties 70
3.4.1 MG J0751+2716 70
3.4.2 JVAS B1938+666 80
3.5 Intrinsic source properties 84
3.5.1 Source plane inversion 84
3.5.2 Source-plane morphology of MG J0751+2716 85
3.5.3 Source-plane morphology of JVAS B1938+666 88
3.6 Resolved molecular gas emission at high redshift 90
3.6.1 CO–H2 conversion factor and molecular gas mass 90
3.6.2 Dynamical masses 91
3.6.3 Gas fractions within dust obscured AGN 92
3.7 Discussion 93
3.7.1 Evidence for extended molecular gas reservoirs 94
3.7.2 Compact stellar cores at high redshift 96
3.8 Conclusions and future outlook 98
4 Proper motion in lensed radio jets at redshift
3: a possible dual super-massive black hole
system in the early Universe 103
4.1 Introduction 104
4.3 Multi-epoch VLBI imaging 111
4.3.1 Observations 111
4.3.2 Data reduction 112
4.3.3 Measurement of the lensed image positions 113
4.3.4 Alignment of the two Epochs 114
4.4 Lens modelling 117
4.4.1 The lensing galaxies have moved 117
4.4.2 The source has moved 118
4.5 Discussion 125
4.5.1 Single AGN scenario 125
4.5.2 Dual AGN scenario 126
4.6 Conclusions and future work 129
5 A novel search for gravitationally lensed radio
sources in wide-field VLBI imaging from the
mJIVE–20 survey 133
5.1 Introduction 134
5.2 Lens candidate selection criteria 136
5.3 Follow-up observations and data reduction 140
5.4 Results 147
5.4.1 Description of the individual lens candidates 147
5.4.2 Testing lens models for the remaining candidates 155
5.5 The lensing statistics of the mJIVE–20 gravitational
lens survey 157
5.6 Prospects for future lens searches with wide-field VLBI 160
5.6.1 Compact lensed radio sources 161
5.6.2 Extended lensed radio sources 164
5.7 Conclusions 164
6 Conclusions and future prospects 185
6.1 The mass density profile of lensing galaxies at
millarcsecond scales 185
6.2 Cold molecular gas at the early stages of galaxy
6.3 Proper motions of SMBH at redshifts > 3 188
6.4 Wide-field VLBI surveys: an efficient way to find
radio-loud lenses 189 6.5 General conclusions 190 6.6 Future prospects 192 Samenvatting 194 Compendio 201 Bibliography 210 Acknowledgements 227
