eMerlin lenses and starbursts from the widest-area Herschel and SCUBA-2 surveys

Stephen Serjeant, July 17th 2007

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

• 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*

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

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.

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

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

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

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

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

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