elizabeth stanway - obergurgl, december 2009 lyman break galaxies as markers for large scale...
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Elizabeth Stanway - Obergurgl, December 2009
Lyman Break Galaxies as Markers for Large Scale
Structure at z=5
Elizabeth StanwayUniversity of Bristol
With Malcolm Bremer, Luke Davies, Matt Lehnert, Mark Birkinshaw, Chris Carilli, Alain Omont
Elizabeth Stanway - Obergurgl, December 2009
The ESO Remote Galaxy Survey
VRI image of CL1037-1243
• 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, ~6500-10000Å
(Douglas et al, 2009, 2010)
Elizabeth Stanway - Obergurgl, December 2009
• 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)
The ESO Remote Galaxy Survey
Elizabeth Stanway - Obergurgl, December 2009
Tip of an Iceberg?
• 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
500 kpc
Examples of Lyman Break galaxy spectra in the z=5.00 field
Overdensities at z=5.00 and z=5.15
Elizabeth Stanway - Obergurgl, December 2009
Moving to Longer Wavelengths
High Redshift Galaxies at Millimetre Wavelengths
• At z=5, 850m 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
Elizabeth Stanway - Obergurgl, December 2009
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
Elizabeth Stanway - Obergurgl, December 2009
Cool Gas at High Redshift
(Stanway et al, 2008)
Elizabeth Stanway - Obergurgl, December 2009
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
Elizabeth Stanway - Obergurgl, December 2009
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
Elizabeth Stanway - Obergurgl, December 2009
LABOCA Observations
• 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
Intensity Coverage
5 arcmin
Elizabeth Stanway - Obergurgl, December 2009
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
Elizabeth Stanway - Obergurgl, December 2009
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 850m limits consistent except at high temperatures (T≈100K)
Mgas/Mdust > 100
Elizabeth Stanway - Obergurgl, December 2009
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)
Elizabeth Stanway - Obergurgl, December 2009
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
Elizabeth Stanway - Obergurgl, December 2009
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
Elizabeth Stanway - Obergurgl, December 2009
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)
Elizabeth Stanway - Obergurgl, December 2009
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.
Elizabeth Stanway - Obergurgl, December 2009
• z=4.92
• 3x109 Msun in H2
• May be detected in two CO transitions
• Peak flux 0.4 mJy
• v = 50 km/s
Preliminary Results
Elizabeth Stanway - Obergurgl, December 2009
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-1 emission line 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
Elizabeth Stanway - Obergurgl, December 2009
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
Elizabeth Stanway - Obergurgl, December 2009
Blank Slide
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