Evidence of a Fast Evolution of the UV Luminosity

Function of LBGs beyond z=6 from a wide and deep HAWK-I Survey

Andrea Grazian

INAF - Osservatorio Astronomico di Roma

M. Castellano, A. Fontana, K. Boutsia, R. Bouwens, S. Cristiani, M. Dickinson, F. Fiore, E.

Giallongo, M. Giavalisco, A. Koekemoer, R, Maiolino, A. Moorwood, N. Menci, M. Nonino, L.

Pentericci, A. Renzini, P. Rosati, S. Salimbeni, P. Santini, E. Vanzella

Goals: •“exploration” of the Universe: observing galaxies,

AGNs and structures up to the earliest phases of the Universe;

• to reconstruct the history of fundamental physical quantites: Star Formation Rate, Stellar Mass,

dust content, morphology, metallicity etc.

•To Understand the physics involved. Develop and constrain theoretical models.Pb#1: How can we derive “physical quantities” from a

handful of photons?

Pb#2: We have to select complete galaxy samples by physical properties and not (only) by photometric criteria.

Motivation of our ESO HAWK-I Large Program:

• z=7 is fashionable; availability of HAWK-I.

• COMPLEMENTARY to deep pencil beam surveys with WFC3

• Beat the cosmic variance: wide area survey.

• Possibility to spectroscopically confirm our z=7 relatively bright candidates

ESO LP 181.A.0717 (P.I. A. Fontana)

HAWK-I is a newly-installed wide-field imager at the Nasmyth A focus of the 8 meter UT4 telescope (ESO, Paranal). It is provided with four 2048x2048 pixels detectors for a total field of view of 7.5'x7.5'. The pixel scale is 0.106".

It has 10 observing filters: 4 broad band filters (Y, J, H & K) and 6 narrow band filters (Bracket gamma, CH4, H2, 1.061 μm, 1.187 μm & 2.090 μm).

Hawk-I Science Verification +ESO LP (HAWK-I+FORS2): (PI A. Fontana)

Deep IR Survey with Hawk-I & WFC3

GOODS-S

BDF4

NTTDF

WFC3 Early Science Release + Illingworth’s UDF data

ACS - Z Hawk-I - Y

WFC3- 1.5hr

Hawk-I 15hr

Hawk-I is a powerful survey machine, even in WFC3 era.

Yband

WFC3 4.7 sq. arcmin

Hawk-I 56.3 sq. arcmin

Hawk-I Y 15hr WFC3-J 22hr

z=6.8z=7

Z band Y band

Lyα UV continuum

Lyman Break Galaxies at z=7

An unexpected , large population of contaminants

To clean the sample: “aggressive”requirement of non-detection in the UBVRI

bands(ALL <2σ; 4 bands <1σ)

ZI

R

V

B

Y

Castellano et al. 2009arxiv:0909.2853

z∼7 candidates in Hawk-I GOODS-S observations

Castellano et al. 2009arxiv:0909.2853

Stacking of z∼7 candidates in Hawk-I GOODS-S

z∼7 candidates in Hawk-I BDF4 and NTTDF fieldY

Y

B+V+I Z Y J+H+K

Hawk-I candidates are consistent with WFC3 observations done so far.

I Z Y105 J125

UDF

Hawk-I

Extract expected galaxies in Extract expected galaxies in your field (Lyour field (LUVUV, , zz))

Extract expected galaxies in Extract expected galaxies in your field (Lyour field (LUVUV, , zz))

Compute Magnitudes (ACompute Magnitudes (AVV, , Lyα)Lyα)

Compute Magnitudes (ACompute Magnitudes (AVV, , Lyα)Lyα)

Place them at random Place them at random position in the imageposition in the imagePlace them at random Place them at random position in the imageposition in the image

Perform multicolor extractionPerform multicolor extractionPerform multicolor extractionPerform multicolor extraction

Retain the fraction selected Retain the fraction selected with your favoured criterionwith your favoured criterionRetain the fraction selected Retain the fraction selected with your favoured criterionwith your favoured criterion

For each set of LF param For each set of LF param (α,L*,(α,L*,φφ))

For each set of LF param For each set of LF param (α,L*,(α,L*,φφ))

RepRepeat eat N N

timetimess

RepRepeat eat N N

timetimess

For GOODS-S, about 104 simulations for 106 galaxies..

“Counting” is not enough... need to evaluate systematics

Castellano et al. 2009arxiv:0909.2853

Hawk-I: bright &rareERS: intermediate

HUDF: faint & numerous

Clear evidence of a fast evolution of the LF from z=6 to z=7

Bunker +09 arxiv:0909.2255

Oesch+ 09 arxiv:0909.1806

Yan+ 09 arxiv:0910.0077

McLure+ 09 arxiv 0909.2437

Candidates @ z ≈ 7 in the WFC3

The SFRD(z): impact of the uncertainties

of WFC3 data.

Bouwens+09, arxiv:0909.1803

Yan+09, arxiv:0910.0077

Summary & Conclusions Galaxies at z=7 and 8 are reliably detected

with new generation IR imagers - Hawk-I and WFC3 are complementary at Y=25-27 - beyond WFC3 wins.

• Data interpretation is complex -requires careful evaluation of instrumental and selection effects.•60 hours of FORS2 already awarded for spectroscopy!!

• Clear evidence for a fast evolution from z=6 to z=7 . beyond is controversial

Castellano et al. 2009 (A&A in press) arXiv:0909.2853