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) 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 pointings across 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

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 microns across 291 pixels with a dispersion of 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

Data Reduction  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  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)

Larger view of pipeline Graphic User Interface

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. ObjectRA (h m s)Dec (d m s)RedshiftFlux 850um /mJy No. of Pointings 8C HzRG C SMM C SMM C SMM C HzRG C60.07 HzRG C41.17 HzRG

8C and its 3 companion submillimetre galaxies SMM1 and SMM2 are roughly aligned with the jet from the radio galaxy (Stevens et al. 2003) HzRGSMM1SMM2SMM3

8C HzRG Halpha

8C SMM1a Halpha

8C SMM1b Halpha

8C SMM2 Halpha

8C SMM3 Halpha

Summary of 8C HzRG and companion galaxies SMM1b – strong Halpha, slightly displaced SMM1a – no convincing detection SMM2 – good Halpha line SMM3 – no convincing detection HzRG – good Halpha line

The other 3 high-redshift radio galaxies 8C Z = C60.07 Z = C41.17 Z = 3.792

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

H-alpha peak is displaced from the expected wavelength, possibly because the dispersion axis is aligned with a companion submillimetre galaxy A closer look at 4C (z=3.788) 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).

S tar 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 > L solar ) 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 Star formation rates and evidence of quasars SourceS (H alpha )L (H alpha )SFR (H alpha )L (FIR)SFR (L FIR ) FWHM (H alpha ) Wm WM solar yr L solar M solar yr -1 km s -1 8C HzRG < C SMM1b < C SMM unresolved 4C60.07 HzRG <

Summary (a)H-alpha emission detected for four galaxies at redshifts 3.5 – 3.8 (b)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 (c)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 (d)The FWHM of the H-alpha lines show strong evidence of dust- shrouded quasar activity in both the radio galaxies

Extra slides

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

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

Larger view of pipeline Graphic User Interface

HzRG

HzRG

HzRG