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Lyman Break Galaxies as Markers for Large Scale Structure at z=5

Lyman Break Galaxies as Markers for Large Scale Structure at z=5. Elizabeth Stanway University of Bristol With Malcolm Bremer, Luke Davies, Matt Lehnert, Mark Birkinshaw, Chris Carilli, Alain Omont. The ESO Remote Galaxy Survey. Targets the 10 EDisCS Survey cluster fields (VRIJK)

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Lyman Break Galaxies as Markers for Large Scale Structure at z=5

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  1. Lyman Break Galaxies as Markers for Large Scale Structure at z=5 Elizabeth Stanway University of Bristol With Malcolm Bremer, Luke Davies, Matt Lehnert, Mark Birkinshaw, Chris Carilli, Alain Omont

  2. The ESO Remote Galaxy Survey • Targets the 10 EDisCS Survey cluster fields (VRIJK) • Adds Z band imaging and 100hrs of spectroscopy • Also Spitzer/IRAC photometry • 20 VLT/FORS2 Slitmasks • Targets R-drops with R-I>1.3, IAB<26.3, z~5 • R~660, l~6500-10000Å (Douglas et al, 2009, 2010) VRI image of CL1037-1243

  3. The ESO Remote Galaxy Survey • Better than 80% spectroscopic completeness for dropout candidates • Reasonable S/N on continuum • 68 Confirmed Redshifts at 4.4<z<6.4 including: • 35 Lyman- emission lines • 33 redshifts determined from Lyman breaks (18 class A, 13 B)

  4. Tip of an Iceberg? Overdensities at z=5.00 and z=5.15 500 kpc • These structures may extend beyond the limits of the imaging fields • One of the fields shows evidence for spatial as well as redshift clustering • Redshift precision is better than 0.002 • The redshift spikes are not in skyline-free wavelength regions Examples of Lyman Break galaxy spectra in the z=5.00 field

  5. Moving to Longer Wavelengths High Redshift Galaxies at Millimetre Wavelengths • At z=5, 850m is close to the dust emission peak (i.e. negative K-correction starting to break down in sub-mm) • Molecular gas is traced at all redshifts by CO emission • The fundamental rotational transition of CO is at 115.271 GHz • CO(1-0) at z=5 is in the 12mm/K band • CO(2-1) emission at z=5 and CO(3-2) at z=8 are both in the 7mm/Ka band • CO(5-2) emission at z=5 is in the 3mm band Also - [CII] is a promising emission line, particularly in low metallicity systems, and can be observed in the 1mm band at z=5-6

  6. Cool Gas at High Redshift • Pilot test • Single pointing at ATCA • 24 hours at 12mm • 44 hours at 7mm • Bandwidth z~0.03 (240 MHz) • Limiting Sensitivity • 0.11 mJy/Beam at 12mm, 0.10 mJy/Beam at 7mm (in 30 km/s) • Angular Resolution • 16x10’’ at 12mm, 7x5’’ at 7mm

  7. Cool Gas at High Redshift (Stanway et al, 2008)

  8. Cool Gas at High Redshift • No detection from LBGs in field => MH2<2x109 Msun BUT • Strong line emission from optically-faint source at 37.64GHz • Likely CO(2-1) at z=5.1245±0.0001 • MH2=2x1010 Msun

  9. Confirming the Line • Reobserved at the NRAO Green Bank Telescope in May 2009 • Observations shallower than planned • Source redetected at 3 • Flux and velocity width consistent with ATCA values

  10. LABOCA Observations Intensity Coverage • APEX/Laboca Observations • 11hrs, June-July 2009, Image r.m.s. = 2.8 mJy • No significant detections of CO Emitter source • No detections of LBGs in field 5 arcmin

  11. Dust Limits on Cluster LBGs • Laboca image covers 4x4 arcmin2 at 90% depth • Can obtain a limit on the dust mass for spectroscopically confirmed z=5 Galaxies in this field • Mstars ~ few x 109 M in these sources • MH2 < few x 109 M (2), based on CO line non-detection • Mdust < few x 108 M (2 limit) at reasonable temperatures

  12. Dust Limits on the CO Source • Mdust < 5 x 108 M (2 limit) at 30K from LABOCA • Mdust < 2 x 108 M (2 limit) at 30K from MAMBO • 1.2mm and 850m limits consistent except at high temperatures (T≈100K) Mgas/Mdust > 100

  13. MAMBO Observations • IRAM 30m MAMBO Observations in April 2009 (4hr) • S1mm = -0.278 ± 0.438 mJy • Implies L’CO/LFIR ratio more akin to lower redshift star-forming galaxies than ULIRGs/SMGs/QSO hosts Figures modified from Solomon & vanden Bout (2005)

  14. Constraints on the SED • SED rules out gas-to-dust ratios typically seen in ULIRGs and QSO hosts at high z. • More like local star-forming galaxies - Normal not exceptional SF galaxy. • ALMA will be able to do this work trivially

  15. Constraints on the SED • SED rules out gas-to-dust ratios typically seen in ULIRGs and QSO hosts at high z. • More like local star-forming galaxies - Normal not exceptional SF galaxy. • ALMA will be able to do this work trivially

  16. Our 2009 ATCA Survey • Targeted second LBG over-density covering 3 times as much area at 37Ghz and 2 GHz bandwidth • Encompasses 7 LBGs in z~0.1 range (around z~4.95), and 1 other z=5.2 source. • Observed each pointing for 2 nights using the ATCA with two 2GHz IFs and 1MHz resolution (at 37GHz). • Redshift coverage of ~4.23-5.34 at 19GHz and ~4.81-5.44 at 37GHz. • RMS limits ~0.2mJy/beam at 19GHz ~0.3mJy/beam at 37GHz (in 1 MHz channels)

  17. Preliminary Results • 6 Possible detections within the ATCA primary beams. • Three detected at 19GHz and three at 37GHz. • One has possible 19 and 37GHz detection. • 3 would fall within the redshift of the over-density. • Two are closely separated in redshift at z~4.6. • Gas masses (H2) ~ 3-6 x109M for 37GHz detection and ~ 3-6 x1010M for 19GHz detections. • FWHM ~50-120kms-1.  Comparable to previous detection.

  18. Preliminary Results • z=4.92 • 3x109 Msun in H2 • May be detected in two CO transitions • Peak flux 0.4 mJy • v = 50 km/s

  19. Limits on LBGs in the Field • All LBGs are not detected at 19GHz or 37GHz. • Image R.M.S. Noise ~ 0.16mJy/beam (at CO(1-0) line) ~ 0.37mJy/beam (at CO(2-1) line) • Gives 2 detection limit ~ LCO< 2.8x1010 K kms-1 pc2 ~ LCO< 1.7x1010 K kms-1 pc2 For an unresolved 200 kms-1emissionline at the redshifts of the galaxies. •  Can constrain molecular gas in LBGs in the field to: M(H2)<2.2x1010 M (2, CO(1-0)) M(H2)<1.4x1010 M (2, CO(2-1)) Total observed mass in stellar component and H2 ~1.3x1011 M in 33.8Mpc3

  20. Conclusions • Lyman Break Galaxies clearly mark out underlying structure at very high redshifts • Regions overdense in LBGs are perfect for follow-up at over wavelengths • Molecular Gas may contribute a substantial fraction of the the baryon mass at z=5 • CO emission lines are currently the most accessible probe of this • Searches for dust and gas dominated galaxies at high z are possible with current instrumentation with several promising candidates already identified • ALMA will enable more complete surveys of the baryon distribution in high z large scale structure

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