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Detection of H-alpha emission from z >3.5 galaxies with AKARI-FUHYU NIR spectroscopy

Detection of H-alpha emission from z >3.5 galaxies with AKARI-FUHYU NIR spectroscopy. Chris Sedgwick Stephen Serjeant Chris Pearson The Open University on behalf of the FUHYU mission program. Phase III FUHYU Mission Program. The FUHYU mission program (PI Chris Pearson)

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Detection of H-alpha emission from z >3.5 galaxies with AKARI-FUHYU NIR spectroscopy

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  1. Detection of H-alpha emission from z>3.5 galaxies withAKARI-FUHYU NIR spectroscopy Chris Sedgwick Stephen Serjeant Chris Pearson The Open University on behalf of the FUHYU mission program

  2. Phase III FUHYU Mission Program • The FUHYU mission program (PI Chris Pearson) • Phase I & II: extensive infrared imaging of well-studied fields • Serjeant et al 2009, Negrello et al 2009, Pearson et al 2010 • Phase III (warm phase): spectroscopy of well-studied sources • In total, 552 spectroscopic pointingsacross 72 sources • For galaxies discussed today, the science objective was to measure rest-frame optical emission lines of star-forming galaxies at very high redshifts 速い 安い 上手い

  3. Observations • IRC NIR instrument (others turned off in warm phase) • N3 imaging filter at 3 microns. Imaging field of view about 10’x10’ (412x512 pixels) with pixel scale of 1.46” and PSF 3.2 pixels • Target guided into the 1’x1’ aperture Np dedicated to spectroscopy • NG grism with wavelength range 2.5 - 5.0 microns across 291 pixels with a dispersion of 0.0097 microns per pixel • AOT IRCZ4 contains 5 initial dark frames, 4 exposure frames for NG, then an N3 reference image, then 4 or more additional NG frames and finally 5 more dark frames • 10 pointings per target wherever possible, each of about 10 minutes

  4. Data Reduction • IRC data reduction pipeline was adapted for the warm phase (Onaka et al 2009) and originally used to reduce our data • However we found it necessary to make bespoke corrections for spacecraft jitter between sub-frames and sky subtraction and de-glitching • We also used routines previously developed for SCUBA for zero-footprint drizzling and noise-weighted feature extraction (Serjeant et al. 2008) • Developed an IDL GUI routine to visualise various elements of the reduction on an interactive basis, and the pointings were optimally combined with noise-weighted co-adding

  5. Larger view of pipeline Graphic User Interface

  6. High-redshift Radio and Submillimetre Galaxies We targeted four high-redshift radio galaxies (redshifts known from Ly-alpha lines), and three submillimetre galaxies believed to be associated with one of them.

  7. 8C1909+722 and its 3 companion submillimetre galaxies HzRG SMM1 SMM2 SMM3 SMM1 and SMM2 are roughly aligned with the jet from the radio galaxy (Stevens et al. 2003)

  8. 8C1909+722 HzRG Halpha

  9. 8C1909+722 SMM1a Halpha

  10. 8C1909+722 SMM1b Halpha

  11. 8C1909+722 SMM2 Halpha

  12. 8C1909+722 SMM3 Halpha

  13. Summary of 8C1909+722 HzRG and companion galaxies HzRG – good Halpha line SMM1a – no convincing detection SMM1b – strong Halpha, slightly displaced SMM2 – good Halpha line SMM3 – no convincing detection

  14. The other 3 high-redshift radio galaxies 8C1435+635 Z = 4.261 4C60.07 Z = 3.788 4C41.17 Z = 3.792

  15. Spectra for other three radio galaxies observed 8C1435_635 (z=4.261)No convincing H-alpha detection 4C60.07 (z=3.788)Broad peak just above expected H-alpha (probable identification) 4C41.17 (z=3.792)No convincing H-alpha detection

  16. A closer look at 4C 60.07 (z=3.788) H-alpha peak is displaced from the expected wavelength, possibly because the dispersion axis is aligned with a companion submillimetre galaxy Spitzer average 3.6 and 4.5 micron images with superimposed SMA 890 micron image and contours. Square is radio galaxy; A and B are submillimetre components. Image from Ivison et al (2008).

  17. Star formation rates and evidence of quasars • Star Formation Rates (SFRs) estimated from the H-alpha lines of these galaxies (using Kennicutt 1998) is a factor of ~20 lower than the SFRs estimated from far infrared luminosity, suggesting strong dust obscuration • Three of these sources are HyLIRGs (L > 1013Lsolar) • The FWHM of the H-alpha line for each of these galaxies is high, particularly for the two radio galaxies, suggesting that dust-shrouded quasars are present

  18. Summary • H-alpha emission detected for four galaxies at redshifts 3.5 – 3.8 • Two submillimetre galaxies are at the same redshift as companion high-redshift radio galaxy, confirming the conclusion by Stevens et al (2003) that they are part of the same extensive star-forming cluster • Star formation rates estimated from H-alpha lines show a decrement by a factor of ~20 from FIR-estimated SFRs suggesting strong dust obscuration in the galaxies • The FWHM of the H-alpha lines show strong evidence of dust-shrouded quasar activity in both the radio galaxies

  19. Extra slides

  20. Extra slide Example of comparison between IRC and OU pipelines (1370153.9) Top: raw spectrum output from IRC pipeline Middle: IRC pipeline with extra sky subtraction and Gaussian across several (spatial) columns Bottom: OU pipeline

  21. Extra slide • Comparison of H-alpha line luminosity with other ULIRGS • ( still work in progress)

  22. Larger view of pipeline Graphic User Interface

  23. HzRG 1370157

  24. HzRG 1370162

  25. HzRG 1370163

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