Speaker
Ms
Samantha Hickey
(University of Hertfordshire)
Description
We present the results of our search for high redshift Lyman-break galaxies over the GOODS-South field. We use
ACS HST data in B, V, i' & z', VLT ISAAC J and Ks, Spitzer 3.6, 4.5, 5.8 and 8.0 micron data in conjunction with
the new HAWK-I Y-band science verification data to search for dropout galxies in the 6<z<9 redshift range.
Candidates were selected on the basis of a colour cut of (Y-J)AB>0.75 and (z'-Y)AB>1.0 for Y and z' drops
respectively. We find no robust Y-drops (z~9) brighter than J(AB)<26.4. In our search for z'-band dropouts
(z~6.5-7.5), we identify two previously-known Galactic T-dwarf stellar contaminants with these colours, and two
likely supernovae seen in the Y-band data. We also identify 2 galaxies with z'-drop colours and bright Spitzer/IRAC
fluxes which are likely z>6.5 galaxies.The implications if all or none of our candidates are real on the Ultra-Violet
luminosity functions at z>6.5 are explored. We find our number of z'-drop candidates to be inconsistent with the
expected number of z' drops in a simple no-evolution scenario from the z=3 Lyman-break galaxy luminosity
function but we are marginally consistent with the observed luminosity function at z approx. 6 (if all our
candidates are real). However, it is possible that one or both of our z'-drop candidates are not z>6.5 galaxies,
which would demand evolution of the luminosity function at early epochs, in the sense that the number density
of UV-luminous star-forming galaxies at z>7 is less than at z=3-6.
Primary author
Ms
Samantha Hickey
(University of Hertfordshire)
Co-authors
Dr
Andrew Bunker
(University of Oxford)
Dr
Matt Jarvis
(University of Hertfordshire)
