pdf - SRON

More documents

Recommendations

Info

CHAPTER 3: SOURCE COUNTS OF THE AXIS SOURCES component so either there is a diffuse component, or the source counts has to steepen again somewhere below the current flux limits. 3.5 Summary In this chapter we have performed a maximum likelihood fit to a broken power law model for the log N − log S in four different energy bands: Soft (0.5-2 keV), Hard (2-10 keV), XID (0.5-4.5 keV) and Ultrahard (4.5-7.5 keV). The results of the fit are summarized in table 3.3. We have found that fits to the source counts using fixed spectral slopes produce similar results to those using the spectral slopes of the individual sources, but with larger error bars. The source counts in the Soft, Hard and XID bands present breaks at fluxes around ∼ 10 −14 cgs. A detailed examination of the ratios between the data and the best fit to this model do not show significant differences in the Soft and XID bands, whereas in the Hard band there seems to be some evidence of another break at ∼ 3 × 10 −15 cgs and several changes of slope. This only happens in the Hard band so it is difficult to tell whether is due to the simplicity of the model (that has to take into account several contributions from different populations at different redshifts) or to calibration uncertainties. The best fit model parameter values obtained are compatible with previous smaller and similar surveys, but the combination of large number of sources and wide flux coverage in this work produce smaller uncertainties in the fitted parameters. The source counts of two HR selected subsamples in the Soft band reveals that the spectrally hard sources (those with HR > −0.2) show no flux break in their log N − log S. This may imply that such hard sources are detected at relatively low redshifts and therefore they show no evolution. We have also used our best fit log N − log S to calculate both the total resolved fraction of the Cosmic X-ray Background (including the contribution from bright sources, table 3.3) and the relative contribution in different flux bins to the total CXB (see Fig.3.7). We have used the estimates of the average CXB intensity in the Soft and Hard bands from [160] and converted them to the XID and Ultrahard bands using a power law spectrum with Γ = 1.4. The total resolved fraction down to the lowest fluxes of our combined sample reaches 88% in the Soft band and 86% in the Hard band (where we have been able to reach deep fluxes usin pencil beam surveys [19]), but it is only 60% in 80
CHAPTER 3: SOURCE COUNTS OF THE AXIS SOURCES the XID band and 25% in the Ultrahard band. The total intensity produced extrapolating our log N − log S to zero flux does not saturate the CXB intensity. Assuming that another flux break occurs just below our detected minimum fluxes, we have estimated the minimum slope needed to reproduce the CXB with only discrete sources obtaining values of 1.85 in the Soft band and 1.84 in the Hard band. If we compare these values with those of the galaxy and AGN source counts from the CDF ([19]), we find that galaxies could easily provide this steepening and, among the AGN population, only the absorbed ones could do so as well. The maximum fractional contribution to the CXB in the Soft, Hard and XID bands comes from sources within a decade around ∼ 10 −14 cgs (where the break in the source counts power law approximately occurs). This is almost 50% of the total contribution in the Soft and Hard bands, which means that medium deep surveys such as AXIS are essential to understand the evolution of the X-ray emission in the Universe up to 10 keV. A recent re-estimation of the Soft and Hard CXB intensities using CDF data [109] finds lower resolved fractions of the CXB than in this work. We have shown that the difference in our results in the Soft band, where it is highest, is only at the ∼1-σ level and that it is due to the different ways in which the CXB intensity is calculated. In [109] they add different contributions at different fluxes, which produces an effective slope Γ ∼ 1.8 which is much steeper than the CXB spectral slope Γ = 1.4 that we have assumed. 81
Page 3:
Universidad de Cantabria Departamen
Page 7:
A mis padres
Page 10 and 11:
explicar las altas luminosidades de
Page 12 and 13:
Además, una importante fracción (
Page 14 and 15:
ealizar estudios de espectroscopía
Page 16 and 17:
distribución diferencial que, al e
Page 18 and 19:
materia sobre el agujero negro cent
Page 20 and 21:
analizadas proviene de fuentes en t
Page 22:
Haciendo uso del segundo catálogo
Page 27:
With magic, you can turn a frog int
Page 30:
Un capítulo aparte merecen mis com
Page 33 and 34:
Summary Since its discovery more th
Page 36 and 37:
xxxiv
Page 38 and 39:
CONTENTS 1.6.1 The K-correction . .
Page 40 and 41:
CONTENTS 5.3.2 Analytical model . .
Page 42 and 43:
LIST OF FIGURES 4.6 Soft 1 − P µ
Page 45 and 46:
Chapter 1 Introduction In the last
Page 47 and 48:
CHAPTER 1: INTRODUCTION have confir
Page 49 and 50:
CHAPTER 1: INTRODUCTION by this mis
Page 51 and 52:
CHAPTER 1: INTRODUCTION Figure 1.2
Page 53 and 54:
CHAPTER 1: INTRODUCTION [161], [242
Page 55 and 56:
CHAPTER 1: INTRODUCTION tant contri
Page 57 and 58:
CHAPTER 1: INTRODUCTION to-noise ra
Page 59 and 60:
CHAPTER 1: INTRODUCTION Compton up-
Page 61 and 62:
CHAPTER 1: INTRODUCTION ([142]). It
Page 63 and 64:
CHAPTER 1: INTRODUCTION (NLR) and i
Page 65 and 66:
CHAPTER 1: INTRODUCTION optically c
Page 67 and 68:
CHAPTER 1: INTRODUCTION ber of AGN
Page 69 and 70:
CHAPTER 1: INTRODUCTION Figure 1.5
Page 71 and 72:
CHAPTER 1: INTRODUCTION 1.7.3 The X
Page 73 and 74: CHAPTER 1: INTRODUCTION AGN are ess
Page 75: CHAPTER 1: INTRODUCTION subjects ma
Page 78 and 79: CHAPTER 2: AGN SURVEYS WITH XMM-New
Page 84 and 85: R R OQP ONM 40 Table 2.1: Continued
Page 99 and 100: Chapter 3 Source counts of the AXIS
Page 101 and 102: CHAPTER 3: SOURCE COUNTS OF THE AXI
Page 105 and 106: 61 Table 3.1 Maximum likelihood fit
Page 123: CHAPTER 3: SOURCE COUNTS OF THE AXI
Page 128 and 129: CHAPTER 4: CLUSTERING OF AXIS AND X
Page 156: CHAPTER 4: CLUSTERING OF AXIS AND X
Page 159 and 160: Chapter 5 Luminosity function of XM
Page 161 and 162: CHAPTER 5: LUMINOSITY FUNCTION OF X
Page 175 and 176:
CHAPTER 5: LUMINOSITY FUNCTION OF X
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 190 and 191:
Page 192 and 193:
CHAPTER 6: SUMMARY OF THE RESULTS s
Page 194 and 195:
CHAPTER 6: SUMMARY OF THE RESULTS b
Page 196 and 197:
CHAPTER 6: SUMMARY OF THE RESULTS F
Page 199 and 200:
Appendix A Sensitivity maps The val
Page 201 and 202:
APPENDIX A: SENSITIVITY MAPS clearl
Page 204 and 205:
APPENDIX A: SENSITIVITY MAPS 160
Page 206 and 207:
REFERENCES [16] Barger, A. J., Cowi
Page 208 and 209:
REFERENCES [61] Ehle, M., Breitfell
Page 210 and 211:
REFERENCES [107] Hawkins, M. R. S.
Page 212 and 213:
REFERENCES [148] Matarrese, S., Col
Page 214 and 215:
REFERENCES [190] Richstone, D., Ahj
Page 216:
REFERENCES [236] Wisotzky, L., 1998
show all

pdf - SRON

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?