emerlin lenses and starbursts from the widest-area herschel and scuba-2 surveys stephen serjeant,...
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![Page 1: EMerlin lenses and starbursts from the widest-area Herschel and SCUBA-2 surveys Stephen Serjeant, July 17th 2007](https://reader035.vdocuments.site/reader035/viewer/2022062715/56649d775503460f94a596e8/html5/thumbnails/1.jpg)
eMerlin lenses and starbursts from the widest-area Herschel and SCUBA-2 surveys
Stephen Serjeant, July 17th 2007
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5 150mJy at 850m over 4000 deg2 (2 years) then the whole JCMT-accessible sky (5 years)
• Find galaxies in the top 2-3 most luminous in the Hubble volume; the complete range of submm galaxy properties
• Determine the bright submm number counts• Determine the gravitational lensing fraction of submm galaxies• Mapping the peaks in the star formation density field (SCUBA-2
follow-up of SASSy sources)• Provide high-resolution foregrounds for Planck• Identify new populations of local cold ultraluminous galaxies
• Provide new submm pointing and flux calibrators
The SCUBA-2 All-Sky Survey
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• Approximately 1200 hours open time key project proposal - a SLOAN for Herschel
• 1000 deg2 SPIRE and PACS survey (110-500m):300 deg2 in SDSS / UKIDSS-LAS NGP
(LOFAR, eMerlin, Hawaii, La Palma)
300 deg2 in KIDS-N
(SKA pathfinders for HI and radio continuum; shallower LOFAR; visible from Atacama, ESO, La Palma)
400 deg2 in KIDS-S
(SKA pathfinders for HI and radio continuum; SPT/SZ surveys; ALMA; GAMA; DES over part)
* = obligatory contrived acronyms under discussion
The Herschel Kilo-Degree open time survey*
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The Herschel Kilo-Degree open time survey*• Local galaxies to 104-5 M of dust
• ~150,000 galaxies at z<0.3; half a million galaxies in total
• Around 1000 strong gravitational lenses; other rare objects
• Fluctuations in the far-IR background• High-resolution imaging of Planck HFI galaxies,
radiogalaxies, and S-Z clusters• Large-scale structure of the submm sky
* = obligatory contrived acronyms under discussion
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Strong lensing predictions
UNLENSED proto-spheroids (black solid line; Granato et al. 2004) IRAS galaxies (starbursts & spirals galaxies Silva et al. 2004, 2005)
radio sources (blazars; De Zotti et al. 2005)
STRONGLY LENSED proto-spheroids (black dashed line; Negrello et al. 2007)
Mattia Negrello, priv. comm.
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Mattia Negrello, priv. comm.
Strong lensing predictions
• Counts of unlensed proto-spheroids– shape of bright (S>100mJy) source counts unknown
• however for the magnifications considered (~10) the sources being magnified are in the constrained region of the counts
– extrapolation of 850m counts to shorter wavelengths • uncertainties mainly at 250-350m, but Granato model reproduces
160m counts
• Modelling of strong lensing– dark matter halo profile
• SIS and NFW have similar integrated magnification distributions less than x2 uncertainty in magnification bias
– presence of satellites and structures not considered• would enhance the lensing probability
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Mattia Negrello, priv. comm.
Strong lensing predictions
5 sensitivities (mJy) 250 m 350 m 500 m
T1000
(hours)
PMode 45 62 53 1168
A = 1000 deg2
250 m 350 m 500 mTime
(hours)
PMode 2984 (1%) 1570 (4%) 741 (35%) 1168
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Simon Dye, priv. comm.
Relative probability that zs=3 galaxy is lensed • Observed lens n(zL) is a convolution of intrinsic n(z) and the probability that a galaxy at z will act as a lens
• Differences due to cosmology are much bigger than differences due to lens model uncertainty
• Plot shows normalized p(zL) but in principle the absolutes give even stronger constraints on
cosmology
Cosmological constraints
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Simon Dye, priv. comm.
Cosmological constraints Method:
1. Create 1000 realisations of n(zL) for a given cosmology (m=0.3, =0.7 in this case)
2. Fit n(zL) for a range of cosmologies3. Vary the redshifts and repeat 1.
Current limitations:
1. Fitting ignores absolute probabilities (e.g. larger makes lensing more likely) can do better
2. Only fixed source redshifts3. Selection effects ignored uncertainties will really be higher
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Simon Dye, priv. comm.
Cosmological constraints 560 lenses, zs=3 560 lenses, zs=6
Degeneracy different to CMB; m better constrained than
0 0.5 1
m
0 0.5 1
m0
0
.5
1
0
0.5
1
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eMerlin imaging
• Confirmation of lensing: the most efficient lensing survey
• Multiple image statistics; lens matter distribution of 0.3<z<1.5 galaxies
• Starburst morphologies• Identifications of ≤ 250m
drop-outs
Confusing sources for eMerlin 1.4GHz snapshots: ~2 sources at ~10mJy per eMerlin primary beam
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