1. Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah

2. Collaborators: Michael Pracy (ANU) Frank Briggs (ANU) Jayaram Chengalur (NCRA) Matthew Colless (AAO) Roberto De Propris (CTIO)

3. Talk Outline Introduction Galaxies and Galaxy Evolution HI 21cm emission & the HI coadding technique Current Observations with the HI coadding technique HI in star forming galaxies at z = 0.24 HI in Abell 370, a galaxy cluster at z = 0.37 Future Observations with SKA pathfinders using ASKAP and WiggleZ using MeerKAT and zCOSMOS

4. What is HI? The many lives of hydrogen HI = neutral atomic hydrogen gas (one proton, one electron) HII = ionised hydrogen gas (one proton) – chemistry H + H 2 = hydrogen molecular gas

5. What is HI? The many lives of hydrogen HI = neutral atomic hydrogen gas (one proton, one electron) HII = ionised hydrogen gas (one proton) – chemistry H + H 2 = hydrogen molecular gas

6. The Significance of HI gas

7. HI Gas and Star Formation Neutral atomic hydrogen gas cloud (HI) molecular gas cloud (H 2 ) star formation

8. Galaxy Types

9. Late-Type Galaxies SpiralIrregular Usually blue in optical colour

10. Early-Type Galaxies EllipticalLenticular (S0) Usually red in optical colour

11. Late-Type Galaxy Spectrum optical spectrum of a late-type galaxy Wavelength (Å) Intensity 4000500060007000 NGC 1832 [OII] HβHβ Hα HγHγ HδHδ [OIII] [SII]

12. Early-Type Galaxy Spectrum line from Doyle & Drinkwater 2006 Wavelength (Å) Intensity 4000500060007000 NGC 1832 [OII] HβHβ Hα HγHγ HδHδ [OIII] [SII] optical spectrum of an early-type galaxy Wavelength (Å) Intensity 4000500060007000 NGC 1832 Mg Ca H & K G band Na

13. Late-Type Galaxy HI 21-cm Spectrum NGC 5701 nearly face-on spiral galaxy Radio Flux Density (mJy)

14. Early-Type Galaxies Little or no neutral atomic hydrogen gas As a consequence little or no active star formation

15. Evolution in Galaxies

16. Galaxy Clusters

17. Galaxy Cluster: Coma

18. Butcher-Oemler Effect

19. The Cosmic Star Formation Rate Density

20. SFRD vs z Hopkins 2004

21. SFRD vs time Hopkins 2004

22. The Cosmic Neutral Gas Density

23. The Cosmic Gas Density vs. Redshift Zwaan et al. 2005 HIPASS HI 21cm Rao et al. 2006 DLAs from MgII absorption Prochaska et al. 2005 DLAs

24. The Cosmic Gas Density vs. Redshift Zwaan et al. 2005 HIPASS HI 21cm Rao et al. 2006 DLAs from MgII absorption Prochaska et al. 2005 DLAs

25. Lyman-α Absorption Systems quasar hydrogen gas clouds Lyman-α emission Lyman-α absorption by clouds Wavelength observer Intensity

26. Damped Lyman-α Lyman-α 1216 Å rest frame Intensity Wavelength (Å) 4200440046004800 50005200 Lyα emission QSO 1425+6039 redshift z = 3.2 Keck HIRES optical spectrum DLA Lyman-α forest

27. The Cosmic Gas Density vs. Redshift Zwaan et al. 2005 HIPASS HI 21cm Rao et al. 2006 DLAs from MgII absorption Prochaska et al. 2005 DLAs

28. HI 21-cm Emission

29. Neutral atomic hydrogen creates 21 cm radiation proton electron

30. Neutral atomic hydrogen creates 21 cm radiation

33. photon

34. Neutral atomic hydrogen creates 21 cm radiation

35. HI 21cm emission HI 21 cm emission decay half life ~10 million years (3  10 14 s) 1 M   2.0  10 33 g  1.2  10 57 atoms of hydrogen atoms total HI gas in galaxies ~ 10 7 to 10 10 M  HI 21 cm luminosity of ~2  10 32 to 2  10 35 ergs s -1 For comparison, in star forming galaxies: luminosity of H  emission ~3  10 39 to 3  10 42 ergs s -1 HI 21 cm emission ~10 7 times less power than H  emission

36. HI 21cm emission HI 21 cm emission decay half life ~10 million years (3  10 14 s) 1 M   2.0  10 33 g  1.2  10 57 atoms of hydrogen atoms total HI gas in galaxies ~ 10 7 to 10 10 M  HI 21 cm luminosity of ~2  10 32 to 2  10 35 ergs s -1 For comparison, in star forming galaxies: luminosity of H  emission ~3  10 39 to 3  10 42 ergs s -1 HI 21 cm emission ~10 7 times less power than H  emission

37. HI 21cm emission HI 21 cm emission decay half life ~10 million years (3  10 14 s) 1 M   2.0  10 33 g  1.2  10 57 atoms of hydrogen atoms total HI gas in galaxies ~ 10 7 to 10 10 M  HI 21 cm luminosity of ~2  10 32 to 2  10 35 ergs s -1 For comparison, in star forming galaxies: luminosity of H  emission ~3  10 39 to 3  10 42 ergs s -1 HI 21 cm emission ~10 7 times less power than H  emission

38. HI 21cm emission HI 21 cm emission decay half life ~10 million years (3  10 14 s) 1 M   2.0  10 33 g  1.2  10 57 atoms of hydrogen atoms total HI gas in galaxies ~ 10 7 to 10 10 M  HI 21 cm luminosity of ~2  10 32 to 2  10 35 ergs s -1 For comparison, in star forming galaxies: luminosity of H  emission ~3  10 39 to 3  10 42 ergs s -1 HI 21 cm emission ~10 7 times less power than H  emission

39. HI 21cm emission HI 21 cm emission decay half life ~10 million years (3  10 14 s) 1 M   2.0  10 33 g  1.2  10 57 atoms of hydrogen atoms total HI gas in galaxies ~ 10 7 to 10 10 M  HI 21 cm luminosity of ~2  10 32 to 2  10 35 ergs s -1 For comparison, in star forming galaxies: luminosity of H  emission ~3  10 39 to 3  10 42 ergs s -1 HI 21 cm emission ~10 7 times less power than H  emission

40. HI 21cm emission HI 21 cm emission decay half life ~10 million years (3  10 14 s) 1 M   2.0  10 33 g  1.2  10 57 atoms of hydrogen atoms total HI gas in galaxies ~ 10 7 to 10 10 M  HI 21 cm luminosity of ~2  10 32 to 2  10 35 ergs s -1 For comparison, in star forming galaxies: luminosity of H  emission ~3  10 39 to 3  10 42 ergs s -1 HI 21 cm emission ~10 7 times less power than H  emission

41. HI 21cm Emission at High Redshift

42. HI 21cm emission at z > 0.1 TelescopeRedshiftObs Time Number and HI Mass of galaxies Who and When WSRTz = 0.18 Abell 2218 200 hours1 galaxy 4.8  10 9 M  Zwaan et al. 2001 VLAz = 0.19 Abell 2192 ~80 hours1 galaxy 7.0  10 9 M  Verheijen et al. 2004 WSRTtwo clusters at z = 0.19 & z = 0.21 420 hours 42 galaxies 5  10 9 to 4  10 10 M  Verheijen et al. 2007 Areciboz = 0.17 to 0.25 2 to 6 hours per galaxy 26 galaxies (2 to 6)  10 10 M  Catinella et al. 2007

43. Coadding HI signals

44. RA DEC Radio Data Cube Frequency HI redshift

45. Coadding HI signals RA DEC Radio Data Cube Frequency HI redshift positions of optical galaxies

46. Coadding HI signals frequency flux

47. Coadding HI signals frequency flux z2 z1 z3

48. Coadding HI signals frequency flux z2 z1 z3 velocity HI signal

49. Current Observations - HI coadding

50. Giant Metrewave Radio Telescope

54. Anglo-Australian Telescope

55. multi-object, fibre fed spectrograph 2dF/AAOmega instrument

56. The Fujita galaxies H  emission galaxies at z = 0.24

57. The Subaru Telescope

58. The Surprime-cam filters H  at z = 0.24

59. Late-Type Galaxy Spectrum optical spectrum of a late-type galaxy Wavelength (Å) Intensity 4000500060007000 NGC 1832 [OII] HβHβ Hα HγHγ HδHδ [OIII] [SII]

60. Intensity Narrowband Filter: Hα detection at z=0.24 AAOmega Spectrum optical red wavelengths

61. The Fujita Galaxies Subaru Field 24’ × 30’ narrow band imaging  Hα emission at z = 0.24 (Fujita et al. 2003, ApJL, 586, L115) 348 Fujita galaxies 121 redshifts using AAT GMRT ~48 hours on field DEC RA

62. SFRD vs z - Fujita Hopkins 2004 Fujita et al. 2003

63. Fujita galaxies - B filter Thumbnails 10’’ sq Ordered by H  luminosity

64. Fujita galaxies - B filter Thumbnails 10’’ sq Ordered by H  luminosity

65. Coadded HI Spectrum

66. HI spectrum all Fujita galaxies neutral hydrogen gas measurement using 121 redshifts - weighted average M HI = (2.26 ± 0.90) ×10 9 M  raw binned

67. The Cosmic Neutral Gas Density

68. my new point The Cosmic Gas Density vs. Redshift

69. my new point Cosmic Neutral Gas Density vs. Time

70. Galaxy HI mass vs Star Formation Rate

71. Galaxy HI Mass vs Star Formation Rate HIPASS & IRAS data z ~ 0 Doyle & Drinkwater 2006

72. HI Mass vs Star Formation Rate at z = 0.24 line from Doyle & Drinkwater 2006 all 121 galaxies

73. HI Mass vs Star Formation Rate at z = 0.24 line from Doyle & Drinkwater 2006 42 bright L(Hα) galaxies 42 medium L(Hα) galaxies 37 faint L(Hα) galaxies

74. Abell 370 a galaxy cluster at z = 0.37

75. Nearby Galaxy Clusters are Deficient in HI Gas

76. HI Deficiency in Clusters Def HI = log(M HI exp. / M HI obs) Def HI = 1 is 10% of expected HI gas expected gas estimate based on optical diameter and Hubble type interactions between galaxies and interactions with the inter-cluster medium removes the gas from galaxies Gavazzi et al. 2006

77. Why target moderate redshift clusters? at moderate redshifts the whole of the galaxy cluster core and its outskirts are within the field of view of a radio telescope (nearby this not the case – one has to target individual galaxies in clusters one by one) around a cluster there are many more galaxies that lie within a single telescope pointing than for a typical field the Butcher-Oemler effect – the increase in the blue fraction of galaxies in cluster cores with redshift – Is there an increase in the gas content as well?

78. Why target moderate redshift clusters? at moderate redshifts the whole of the galaxy cluster core and its outskirts are within the field of view of a radio telescope (nearby this not the case – one has to target individual galaxies in clusters one by one) around a cluster there are many more galaxies that lie within a single telescope pointing than for a typical field the Butcher-Oemler effect – the increase in the blue fraction of galaxies in cluster cores with redshift – Is there an increase in the gas content as well?

79. Why target moderate redshift clusters? at moderate redshifts the whole of the galaxy cluster core and its outskirts are within the field of view of a radio telescope (nearby this not the case – one has to target individual galaxies in clusters one by one) around a cluster there are many more galaxies that lie within a single telescope pointing than for a typical field the Butcher-Oemler effect – the increase in the blue fraction of galaxies in cluster cores with redshift – Is there an increase in the gas content as well?

80. Abell 370, a galaxy cluster at z = 0.37 large galaxy cluster of order same size as Coma optical imaging ANU 40 inch telescope spectroscopic follow- up with the AAT GMRT ~34 hours on cluster

81. Abell 370 galaxy cluster 324 galaxies 105 blue (B-V  0.57) 219 red (B-V > 0.57) Abell 370 galaxy cluster

82. 3σ extent of X-ray gas R 200  radius at which cluster 200 times denser than the general field

83. The Problem of Galaxy Sizes and the GMRT

84. Galaxy Sizes GMRT has long baselines between dishes (up to 26 km) provides high resolution (~3 arcsec) so that the galaxies are resolved – i.e. they are not point sources for coadding the HI signal I want the galaxies to be unresolved as I can not see the size of individual galaxies for the Fujita galaxies I used an estimate of the HI size from the optical properties of spiral and irregular field galaxies and then smoothed radio data – i.e. make the galaxies unresolved

85. Galaxy Sizes GMRT has long baselines between dishes (up to 26 km) provides high resolution (~3 arcsec) so that the galaxies are resolved – i.e. they are not point sources for coadding the HI signal I want the galaxies to be unresolved as I can not see the size of individual galaxies for the Fujita galaxies I used an estimate of the HI size from the optical properties of spiral and irregular field galaxies and then smoothed radio data – i.e. make the galaxies unresolved

86. Galaxy Sizes GMRT has long baselines between dishes (up to 26 km) provides high resolution (~3 arcsec) so that the galaxies are resolved – i.e. they are not point sources for coadding the HI signal I want the galaxies to be unresolved as I can not see the size of individual galaxies for the Fujita galaxies I used an estimate of the HI size from the optical properties of spiral and irregular field galaxies and then smoothed radio data – i.e. make the galaxies unresolved

87. Galaxy Sizes GMRT has long baselines between dishes (up to 26 km) provides high resolution (~3 arcsec) so that the galaxies are resolved – i.e. they are not point sources for coadding the HI signal I want the galaxies to be unresolved as I can not see the size of individual galaxies for the Fujita galaxies I used an estimate of the HI size from the optical properties of spiral and irregular field galaxies and then smoothed radio data – i.e. make the galaxies unresolved

88. Complication The Abell 370 galaxies are a mixture of early and late types in a variety of environments. My solution make multiple measurements of the HI gas content of the coadded galaxies using a variety of resolutions

89. Complication The Abell 370 galaxies are a mixture of early and late types in a variety of environments. My solution is to make multiple measurements of the HI gas content of the coadded galaxies using a variety of resolutions

90. HI mass 324 galaxies 219 galaxies 105 galaxies 94 galaxies 168 galaxies 156 galaxies 110 galaxies 214 galaxies

91. HI mass 324 galaxies 219 galaxies 105 galaxies 94 galaxies 168 galaxies 156 galaxies 110 galaxies 214 galaxies

92. HI mass 324 galaxies 219 galaxies 105 galaxies 94 galaxies 168 galaxies 156 galaxies 110 galaxies 214 galaxies

93. HI mass 324 galaxies 219 galaxies 105 galaxies 94 galaxies 168 galaxies 156 galaxies 110 galaxies 214 galaxies

94. HI mass 324 galaxies 219 galaxies 105 galaxies 94 galaxies 168 galaxies 156 galaxies 110 galaxies 214 galaxies

95. HI all spectrum all Abell 370 galaxies neutral hydrogen gas measurement using 324 redshifts – large smoothing M HI = (6.6 ± 3.5) ×10 9 M 

96. HI blue outside x-ray gas blue galaxies outside of x-ray gas measurement of neutral hydrogen gas content using 94 redshifts – large smoothing M HI = (23.0 ± 7.7) ×10 9 M 

97. Comparisons with the Literature

98. Average HI Mass Comparisons with Coma

99. Abell 370 and Coma Comparison 214 galaxies 324 galaxies 110 galaxies

100. Abell 370 and Coma Comparison 214 galaxies 324 galaxies 110 galaxies

101. Abell 370 and Coma Comparison 214 galaxies 324 galaxies 110 galaxies

102. HI Density Comparisons

103. HI density field

107. HI density - inner regions of clusters within 2.5 Mpc of cluster centers

108. HI Mass to Light Ratios

109. HI mass to optical B band luminosity for Abell 370 galaxies Uppsala General Catalog Local Super Cluster (Roberts & Haynes 1994)

110. HI Mass to Light Ratios HI mass to optical B band luminosity for Abell 370 galaxies Uppsala General Catalog Local Super Cluster (Roberts & Haynes 1994)

111. Galaxy HI mass vs Star Formation Rate

112. Galaxy HI Mass vs Star Formation Rate HIPASS & IRAS data z ~ 0 Doyle & Drinkwater 2006

113. HI Mass vs Star Formation Rate in Abell 370 all 168 [OII] emission galaxies line from Doyle & Drinkwater 2006 Average

114. HI Mass vs Star Formation Rate in Abell 370 81 blue [OII] emission galaxies line from Doyle & Drinkwater 2006 87 red [OII] emission galaxies Average

115. Future Observations - HI coadding with SKA Pathfinders

116. SKA – Square Kilometer Array final site decision by 2012?? – money will be the deciding factor both South Africa and Australia are building SKA pathfinder telescopes to strengthen their case for site selection – telescopes also do interesting science SKA promises both high sensitivity with wide field of view possible SKA sites – South Africa and Australia

117. SKA – Square Kilometer Array final site decision by 2012?? – money will be the deciding factor both South Africa and Australia are building SKA pathfinder telescopes to strengthen their case for site selection – telescopes also do interesting science SKA promises both high sensitivity with wide field of view possible SKA sites – South Africa and Australia

118. SKA – Square Kilometer Array final site decision by 2012?? – money will be the deciding factor both South Africa and Australia are building SKA pathfinder telescopes to strengthen their case for site selection – telescopes also do interesting science SKA promises both high sensitivity with wide field of view possible SKA sites – South Africa and Australia

119. SKA – Square Kilometer Array final site decision by 2012?? – money will be the deciding factor both South Africa and Australia are building SKA pathfinder telescopes to strengthen their case for site selection – telescopes also do interesting science SKA promises both high sensitivity with wide field of view possible SKA sites – South Africa and Australia

120. Why South Africa and Australia?

121. Global Population Density

122. Population Density – South Africa

123. Population Density – Australia

124. Radio Interference 10 8 10 9 Frequency (Hz) Log Scales

125. Radio Interference 10 8 10 9 Frequency (Hz) HI at z = 0.4 HI at z = 1.0 Log Scales

126. The SKA pathfinders

127. ASKAP

128. MeerKAT South African SKA pathfinder

129. ASKAP and MeerKAT parameters ASKAPMeerKAT Number of Dishes 4580 Dish Diameter 12 m Aperture Efficiency 0.8 System Temp. 35 K30 K Frequency range 700 – 1800 MHz500 – 2500 MHz Instantaneous bandwidth 300 MHz512 MHz Field of View: at 1420 MHz (z = 0) at 700 MHz (z = 1) 30 deg 2 1.2 deg 2 4.8 deg 2 Maximum Baseline Length 8 km10 km

130. ASKAP and MeerKAT parameters ASKAPMeerKAT Number of Dishes 4580 Dish Diameter 12 m Aperture Efficiency 0.8 System Temp. 35 K30 K Frequency range 700 – 1800 MHz500 – 2500 MHz Instantaneous bandwidth 300 MHz512 MHz Field of View: at 1420 MHz (z = 0) at 700 MHz (z = 1) 30 deg 2 1.2 deg 2 4.8 deg 2 Maximum Baseline Length 8 km10 km

131. ASKAP and MeerKAT parameters ASKAPMeerKAT Number of Dishes 4580 Dish Diameter 12 m Aperture Efficiency 0.8 System Temp. 35 K30 K Frequency range 700 – 1800 MHz500 – 2500 MHz Instantaneous bandwidth 300 MHz512 MHz Field of View: at 1420 MHz (z = 0) at 700 MHz (z = 1) 30 deg 2 1.2 deg 2 4.8 deg 2 Maximum Baseline Length 8 km10 km z = 0.4 to 1.0 in a single observation z = 0.2 to 1.0 in a single observation

132. single pointing assumes no evolution in the HI mass function (Johnston et al. 2007) z = 0.45 to 1.0 980 MHz to 700 MHz one year observations (8760 hours) Simulated ASKAP HI detections

133. MeerKAT HI direct detections MeerKAT will detect galaxies in less time than ASKAP – due to its higher sensitivity by ~2 times – it will still take a long time to detect galaxies at z = 1.0 - perhaps in around a quarter of a year however at a particular redshift in a single pointing, MeerKAT will end up with fewer total detections – due to MeerKAT`s smaller field of view MeerKAT has a larger instantaneous bandwidth of 512 MHz – observe from z = 0.2 to z = 1.0 in single observation (1200 MHz to 700 MHz) MeerKAT’s field of view is better matched to many current optical and other wavelength surveys

134. MeerKAT HI direct detections MeerKAT will detect galaxies in less time than ASKAP – due to its higher sensitivity by ~2 times – it will still take a long time to detect galaxies at z = 1.0 - perhaps in around a quarter of a year however at a particular redshift in a single pointing, MeerKAT will end up with fewer total detections – due to MeerKAT`s smaller field of view MeerKAT has a larger instantaneous bandwidth of 512 MHz – observe from z = 0.2 to z = 1.0 in single observation (1200 MHz to 700 MHz) MeerKAT’s field of view is better matched to many current optical and other wavelength surveys

135. MeerKAT HI direct detections MeerKAT will detect galaxies in less time than ASKAP – due to its higher sensitivity by ~2 times – it will still take a long time to detect galaxies at z = 1.0 - perhaps in around a quarter of a year however at a particular redshift in a single pointing, MeerKAT will end up with fewer total detections – due to MeerKAT`s smaller field of view MeerKAT has a larger instantaneous bandwidth of 512 MHz – observe from z = 0.2 to z = 1.0 in single observation (1200 MHz to 700 MHz) MeerKAT’s field of view is better matched to many current optical and other wavelength surveys

136. MeerKAT HI direct detections MeerKAT will detect galaxies in less time than ASKAP – due to its higher sensitivity by ~2 times – it will still take a long time to detect galaxies at z = 1.0 - perhaps in around a quarter of a year however at a particular redshift in a single pointing, MeerKAT will end up with fewer total detections – due to MeerKAT`s smaller field of view MeerKAT has a larger instantaneous bandwidth of 512 MHz – observe from z = 0.2 to z = 1.0 in single observation (1200 MHz to 700 MHz) MeerKAT’s field of view is better matched to many current optical and other wavelength surveys

137. What I could do with the SKA pathfinders using optical coadding of HI if you gave them to me TODAY.

138. WiggleZ and zCOSMOS WiggleZzCOSMOS Instrument/TelescopeAAOmega on the AATVIMOS on the VLT Target Selection ultraviolet using the GALEX satellite optical I band I AB < 22.5 Survey Area 1000 deg 2 total 7 fields minimum size of ~100 deg 2 COSMOS field single field ~2 deg 2 Primary Redshift Range 0.5 < z < 1.00.1 < z < 1.2 Survey Timeline2006 to 20092005 to 2008 n z by survey end176,00020,000 n z in March 2008~62,000~10,000

139. WiggleZ and zCOSMOS WiggleZzCOSMOS Instrument/TelescopeAAOmega on the AATVIMOS on the VLT Target Selection ultraviolet using the GALEX satellite optical I band I AB < 22.5 Survey Area 1000 deg 2 total 7 fields minimum size of ~100 deg 2 COSMOS field single field ~2 deg 2 Primary Redshift Range 0.5 < z < 1.00.1 < z < 1.2 Survey Timeline2006 to 20102005 to 2008 n z by survey end176,00020,000 n z in March 2008~62,000~10,000

140. WiggleZ and zCOSMOS WiggleZzCOSMOS Instrument/TelescopeAAOmega on the AATVIMOS on the VLT Target Selection ultraviolet using the GALEX satellite optical I band I AB < 22.5 Survey Area 1000 deg 2 total 7 fields minimum size of ~100 deg 2 COSMOS field single field ~2 deg 2 Primary Redshift Range 0.5 < z < 1.00.1 < z < 1.2 Survey Timeline2006 to 20102005 to 2008 n z by survey end176,00020,000 n z in March 2008~62,000~10,000

141. WiggleZ and ASKAP

142. WiggleZ field data as of July 2008 z = 0.45 to 1.0 ASKAP beam size Diameter 6.2 degrees Area 30 deg 2 square ~10 degrees across

143. ASKAP & WiggleZ 100hrs n z = 5072

144. ASKAP & WiggleZ 100hrs n z = 5072

145. ASKAP & WiggleZ 100hrs n z = 5072

146. ASKAP & WiggleZ 1000hrs n z = 5072

147. zCOSMOS and MeerKAT

148. zCOSMOS field data as of March 2008 z = 0.2 to 1.0 7118 galaxies MeerKAT beam size at 1420 MHz z = 0 MeerKAT beam size at 1000 MHz z = 0.4 square ~1.3 degrees across

149. MeerKAT & zCOSMOS 100hrs n z = 3559 half the number of redshift

150. MeerKAT & zCOSMOS 100hrs n z = 3559

151. MeerKAT & zCOSMOS 100hrs n z = 3559

152. MeerKAT & zCOSMOS 1000hrs n z = 3559

153. HI Science with SKA Pathfinders at High z

154. provide constraints on the HI mass function with redshift (the distribution of galaxies with HI mass) – won’t get information on smaller HI systems – need SKA for that begin to trace how gas content varies in different environments with redshift test star formation rate – HI correlation in the period of extreme star formation activity in the universe won’t get galaxy velocity field information – again need SKA

155. HI Science with SKA Pathfinders at High z provide constraints on the HI mass function with redshift (the distribution of galaxies with HI mass) – won’t get information on smaller HI systems – need SKA for that begin to trace how gas content varies in different environments with redshift test star formation rate – HI correlation in the period of extreme star formation activity in the universe won’t get galaxy velocity field information – again need SKA

156. HI Science with SKA Pathfinders at High z provide constraints on the HI mass function with redshift (the distribution of galaxies with HI mass) – won’t get information on smaller HI systems – need SKA for that begin to trace how gas content varies in different environments with redshift test star formation rate – HI correlation in the period of extreme star formation activity in the universe won’t get galaxy velocity field information – again need SKA

157. HI Science with SKA Pathfinders at High z provide constraints on the HI mass function with redshift (the distribution of galaxies with HI mass) – won’t get information on smaller HI systems – need SKA for that begin to trace how gas content varies in different environments with redshift test star formation rate – HI correlation in the period of extreme star formation activity in the universe won’t get galaxy velocity field information – again need SKA

158. Conclusion

159. one can use coadding with optical redshifts to make measurement of the HI 21 cm emission from galaxies at redshifts z > 0.1 using this method we have measured the cosmic neutral gas density at z = 0.24 and have shown that the value is consistent with that from damped Lyα measurements galaxy cluster Abell 370 at z = 0.37 has significantly more gas than similar clusters at z ~ 0 the SKA pathfinders ASKAP and MeerKAT can measure HI 21 cm emission from galaxies out to z = 1.0 using the coadding technique with existing optical redshift surveys Conclusion