DETECTING FAINT SUBMM GALAXIES

USING RADIO LENSING

THE CASE OF THE CLUSTER MS0451

Dr. Léon Koopmans (Kapteyn Institute)Prof. Mike Garrett (ASTRON)

Dr. Olaf Wucknitz ( AIfA Bonn)

OZ Lens 2008, Sydney (Australia)

Alicia Berciano Alba (Kapteyn Institute)

The relevance of dust obscured galaxies

Optical/UV lightIR/submm

dust re-radiated light

~ 50% of the total radiation in the

universe

Critically important to understand galaxy

formation and evolution

dust obscured galaxies

Starburst galaxy SED

dust re-radiated

Submm-galaxies in a nutshell SMGs = dusty, FIR luminous starburst galaxies at high redshift Discovered with SCUBA (JCMT) at 850 mm (Smail, Ivison & Blain 1997)

Bright SMGs(what we can see)

Faint SMGs(the unknown territories)

2 mJy SCUBA’s confussion limit

at 850 mm

Properties of bright SMGs:• Median redshift ~ 2.3• LFIR > 1012 Lsun

ULIRGs • SFR ~103 Msun/yr• Gas-rich mergers• Dust temperature ~

35K• Mgas ~ 1010 – 1011 Msun

Bulk of the submm background

energy at 850 mm(Knudsen , van der Werf & Kneib 2007)

My lab rat : MS0451.6 - 0305

Once upon a time … Borys et al. 2004

Data: Optical : HST F702W, F775W, F850LP NIR (circles) : CFHT JHK’- band Submm (contours): SCUBA 850 mm

Source plane

ERO B

ERO CLBG

~ 10 Kpc

Image plane

Redshifts: LBG ARC1 : z = 2.911 (VLT spectroscopy) EROs* B,C : z = 2.85 (lens model)

*Extremely Red Objects

MERGER!!!

Radio interferometry to the rescue

FIR

Submm

dust re-processed UV radiation from massive stars

synchrotron emmision from electrons generated by SN

Radio

FIR (submm)Massive star

formation

Radio interferometry High resolution “version” of the submm map

High-z starburst:Observed in submm = emitted in FIR

Radio observations :

VLA 1.4GHz (20 cm)

B-array (Berciano Alba et al. 2007)

2 x 4 hours (9th and 10th June 2002)Project ID AN109, PI: NakanishiResolution: 6.34” x 4.87” pa= 7.73

A-array2 x 6 hours (5th and 10th Feb 2006)Resolution: 2.07” x 1.58” pa= -1.19

Data reduction: AIPS + ParselTongue

A+B array naturaly weighted 1.4GHz map

Resolution = 2.78 x 2.18 arcsecs pa=-0.21 rms noise = 10.16 mJy/beam

Grey scale: 3 x noiseContours: 4, 5, 6, 8 and 10 x noise

CR1

CR2

Radio detections located withing the submm emission

4 detections: RJ, E1, E2, E32 tentative detections: C1, C2

SNR ~ 6

SNR ~ 4.5

SNR ~ 4.6SNR ~ 6

SNR ~ 11

SNR ~ 5

(flux ~ 34 mJy)

(flux ~ 23 mJy)

(flux ~ 28 mJy) (flux ~ 42 mJy)

(flux ~ 170 mJy)

(flux ~ 52 mJy)

CR1

CR2

Multi-wavelenght counterparts of the radio detections

AlignmentRadio and NIR map aligned respect to the HST map Radio: 13 sources, rms distance = 0.29” NIR: 93 sources, rms distance = 0.06”

Data Optical: HST ACS F814W ( Moran et al 2007 ) NIR: Subaru CISCO K’-band ( Takata et al 2003 )

Positional Errors Radio: FWHM / (2*SNR) between 0.1” and 0.3” NIR: 0.2” (fitting error for the standard stars used for the astrometry)

White contours: 20cm radio emissionBlue squares: NIR sources Yellow squares: optical arcs produced by a LBG

zphoto = 0.45

Source plane

ERO B

ERO CLBG

~ 10 Kpc

MERGER!!!

Extended source: ~ 3 beams (~ 6”) Peak not consistent with any optical counterpart mayor axis aligned with a posible cluster member

zphoto = 0.4

AGN + radio jet

Not associated with the lensed submm

emission!!!

Radio vs submm emission

Radio contours = 3,4,5,6 and 7 x 30 mJy/beam

CONCLUSIONS ON MS0451 (so far…)

The brightest radio detection (RJ) is not related with the lensed submm emission (probably an AGN jet)

The other radio detections (E1,E2,E3,CR1,CR2) are counterparts of the submm emission

2 radio detections (E1,E2) confirm that ERO B is associated with the submm emission

2 tentative radio detections (CR1,CR2) support the merger hypothesis

THE FUTURE The coming years will see a revolution in

radio / mm interferometric observations: EVLA, eMERLIN, ALMA, SKA, LOFAR…

Window to study high redshift dust obscured universe unnaccesible in optical

Time to think about robust multiwavelenght source reconstruction