Evidence of a Fast Evolution of the UV Luminosity
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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.

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Andrea Grazian INAF - Osservatorio Astronomico di Roma

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Andrea grazian inaf osservatorio astronomico di roma

Evidence of a Fast Evolution of the UV LuminosityFunction 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


Andrea grazian inaf osservatorio astronomico di roma

  • 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.


Andrea grazian inaf osservatorio astronomico di roma

  • 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)


Andrea grazian inaf osservatorio astronomico di roma

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).


Andrea grazian inaf osservatorio astronomico di roma

BDF4

GOODS-S

NTTDF

Deep IR Survey with Hawk-I & WFC3

Hawk-I Science Verification

+

ESO LP (HAWK-I+FORS2):

(PI A. Fontana)

WFC3 Early Science Release + Illingworth’s UDF data


Andrea grazian inaf osservatorio astronomico di roma

ACS - Z

Hawk-I - Y

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

Yband

WFC3- 1.5hr

Hawk-I 15hr

WFC3 4.7 sq. arcmin

Hawk-I 56.3 sq. arcmin


Andrea grazian inaf osservatorio astronomico di roma

Hawk-I Y 15hr

WFC3-J 22hr


Andrea grazian inaf osservatorio astronomico di roma

Z band

z=6.8

Y band

z=7

Lyman Break Galaxies at z=7

UV continuum

Lyα


Andrea grazian inaf osservatorio astronomico di roma

An unexpected , large population of contaminants

Y

V

B

R

I

Z

To clean the sample: “aggressive”

requirement of non-detection in the UBVRI bands

(ALL <2σ; 4 bands <1σ)


Andrea grazian inaf osservatorio astronomico di roma

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

Castellano et al. 2009

arxiv:0909.2853


Andrea grazian inaf osservatorio astronomico di roma

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

Castellano et al. 2009

arxiv:0909.2853


Andrea grazian inaf osservatorio astronomico di roma

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

Y

Y


Andrea grazian inaf osservatorio astronomico di roma

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

I

Z

Y105

J125

UDF

B+V+I

Z

Y

J+H+K

Hawk-I


Andrea grazian inaf osservatorio astronomico di roma

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

For each set of LF param (α,L*,φ)

Extract expected galaxies in your field (LUV, z)

Repeat N times

Compute Magnitudes (AV, Lyα)

Place them at random position in the image

Perform multicolor extraction

Retain the fraction selected with your favoured criterion

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


Andrea grazian inaf osservatorio astronomico di roma

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

Castellano et al. 2009

arxiv:0909.2853

Hawk-I: bright &rare

ERS: intermediate

HUDF: faint & numerous


Andrea grazian inaf osservatorio astronomico di roma

Candidates @ z ≈ 7 in the WFC3

Bunker +09 arxiv:0909.2255

Oesch+ 09 arxiv:0909.1806

Yan+ 09 arxiv:0910.0077

McLure+ 09 arxiv 0909.2437


Andrea grazian inaf osservatorio astronomico di roma

Bouwens+09, arxiv:0909.1803

The SFRD(z): impact of the uncertainties of WFC3 data.

Yan+09, arxiv:0910.0077


Andrea grazian inaf osservatorio astronomico di roma

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


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