Galaxies are composed of four basic materials: stars, gas, dust, and dark-matter. The first three can be seen. The dark matter is required to explain the distribution and movement of the visible components, but has not been directly observed. Both the stars and the gas are composed mainly of Hydrogen, while the dust is mostly silicates, and nobody knows exactly what the dark matter is. Elliptical galaxies usually have little gas or dust, and appear to be mostly stars. Spiral galaxies, on the other hand, tend to have lots of gas, and may have quite a bit of dust, as well as the visible stars. The situation is less clear for the other types of galaxies. ...

Zie: Summary

Lane, Wendy Meredith,

English

Lane, Wendy Meredith

University of Groningen Research Database

  
 University of Groningen
HI 21cm absorbers at moderate redshifts
Lane, Wendy Meredith
IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from
it. Please check the document version below.
Document Version
Publisher's PDF, also known as Version of record
Publication date:
2000
Link to publication in University of Groningen/UMCG research database
Citation for published version (APA):
Lane, W. M. (2000). HI 21cm absorbers at moderate redshifts Groningen: s.n.
Copyright
Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the
author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).
Take-down policy
If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately
and investigate your claim.
Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the
number of authors shown on this cover page is limited to 10 maximum.
Download date: 11-02-2018
HI 21CM ABSORBERS AT MODERATE REDSHIFTS

RIJKSUNIVERSITEIT GRONINGEN
HI 21cm Absorbers at Moderate Redshifts
PROEFSCHRIFT
ter verkrijging van het doctoraat in de
Wiskunde en Natuurwetenschappen
aan de Rijksuniversiteit Groningen
op gezag van de
Rector Magnificus, dr. D.F.J. Bosscher
in het openbaar te verdedigen op
maandag 9 oktober 2000
om 14.15 uur
door
Wendy Meredith Lane
geboren op 23 augustus 1974
te Winchester, MA, USA
Promotor: prof. dr. F.H. Briggs
Beoordelingscomissie: prof. dr. A.G. de Bruyn
prof. dr. R. Sancisi
prof. dr. R.H. Sanders
ISBN 90-367-1301-3
”To see a world in a grain of sand
And a heaven in a wildflower
Hold infinity in the palm of your hand
And eternity in an hour....”
—William Blake
Auguries of Innocence
Cover Image: Ethereal Blue, graphics by Jim Grant.
Digital imagery c1999, PhotoDisc, Inc.
Contents
1 Introduction 11
1.1 H I Gas in Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.2 QSO Absorption Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.3 Tracing the Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.4 A Brief Outline of This Thesis . . . . . . . . . . . . . . . . . . . . . . . . 15
2 The 21cm Survey: Data 19
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2 The Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2.1 Sample Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2.2 Data Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2.3 Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.3 Noise Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.4 The Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.4.1 Notes on Selected Individual Sight Lines . . . . . . . . . . . . . 29
2.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3 Survey Statistics 45
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.2 21cm Detection Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.3 Metal-Line Properties of the Sample . . . . . . . . . . . . . . . . . . . . 49
3.3.1 Metal-Line Rest Equivalent Widths . . . . . . . . . . . . . . . . . 49
3.3.2 Mg II W2796o Distribution . . . . . . . . . . . . . . . . . . . . . . 52
3.3.3 Mg I W2852o and the Mg II Doublet Ratio . . . . . . . . . . . . . . 52
3.3.4 Fe II W2600o Considerations . . . . . . . . . . . . . . . . . . . . . 54
3.4 Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.4.1 Detection Probabilities . . . . . . . . . . . . . . . . . . . . . . . . 55
3.4.2 n21cm(z) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.4.3 Ω21cm(z) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
8 CONTENTS
4 The Absorbers 63
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.2 Deriving the Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.3 B 0248+430, zabs = 0:3941 . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.4 B 0738+313, zabs = 0:2212 . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.5 B 1127 145, zabs = 0:3127 . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.6 Spin Temperature in Redshifted Systems . . . . . . . . . . . . . . . . . . 71
5 A z = 0:0912 H I 21cm Absorber 77
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.2 Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.2.1 WHT/ISIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.2.2 VLA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.2.3 VLBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.2.4 Arecibo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.2.5 WSRT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.3 H I Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.3.1 The Covering Factor of the Gas . . . . . . . . . . . . . . . . . . . 85
5.3.2 Kinetic Temperature . . . . . . . . . . . . . . . . . . . . . . . . . 86
5.3.3 H I Gas in Two Temperature Phases . . . . . . . . . . . . . . . . 87
5.3.4 Discussion of Warm Phase H I Gas . . . . . . . . . . . . . . . . . 89
5.4 H I Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.4.1 Limits on MH I . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
A The U/V Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
B The Delay Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
C Positional Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
6 The Host Galaxies of H I 21cm Absorbers 97
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
6.2 B 0738+313 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
6.2.1 The Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
6.2.2 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
6.2.3 The zabs = 0:2212 Host Galaxy . . . . . . . . . . . . . . . . . . . 101
6.2.4 The zabs = 0:0912 Candidate Host Galaxy . . . . . . . . . . . . . 102
6.3 B 1127 145 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
6.3.1 The Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
6.3.2 Objects in the Field . . . . . . . . . . . . . . . . . . . . . . . . . . 104
6.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
7 Summary and Future Work 111
7.1 Survey and Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
7.2 Individual Absorber Properties . . . . . . . . . . . . . . . . . . . . . . . 112
7.3 On-going and Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 115
CONTENTS 9
Nederlandse Samenvatting 117
English Summary 125
Acknowledgements 133



HI 21cm absorbers at moderate redshifts

Abstract

Similar works

Full text

Available Versions

University of Groningen Research Database

ARTS repository - University of Groningen

University of Groningen

ARTS repository - University of Groningen

University of Groningen Digital Archive

NARCIS