Expanding the Search for Galaxies at z~7

Expanding the Search for
Galaxies at z~7-10 with New
NICMOS Parallel Fields
Alaina Henry (UCLA)
Matt Malkan, Brian Siana, Matthew Ashby, Carrie Bridge,
Ranga-Ram Chary, James Colbert, Mauro Giavalisco, Harry
Teplitz, Patrick McCarthy
The First Galaxies: The initial conditions
of galaxy evolution
 Clues point to z > 7 as important
 Mature and massive galaxies at z~6 (some have
1010 M and ages of a few 100 Myrs; Eyles et al. 2005,
2007; Yan et al. 2006)
 Star formation at z>7 needed for reionization?
Lyman Break Galaxies at z~7
Deep near infrared data needed
Wide area surveys for z>7
 GOODS-S and ESO Remote Galaxy Survey
cover ~150 + 225 arcmin2 (Mannucci et al.
2007; Stanway et al. 2008)
 Upper limit consistent with z~6
 NICMOS Parallel Imaging Survey (Henry et al.
2007, 2008)
 Advantage: Space based IR sensitivity
A z~9 candidate?
 Spitzer/IRAC followup of
NICMOs Parallel Survey
 Very Tentative!
 Efforts to confirm?
 Would imply an LF and
cosmic SFR density
similar to z~3
Pencil beam surveys are now
uncovering galaxies at z>7
Bouwens et al. (2008)
Lensing Surveys for z>7 galaxies
Bouwens et al. z~6
 Richard et al. (2008)
report 10 possible
z~7 candidates
 Bouwens et al.
(2008) argue that
none are z~7
Bouwens et al. z~7
Richard et al. (2008)
New NICMOS Parallel Observations
Increases deep
by 60%
+ 2 fields in SSA22
Total: 14.4 arcmin2
Sensitivities: J110 = 26.027.5 AB
Selection of z>7 candidates
(Only four sources undetected at bands shorter than z)
No z>7 candidates found
The UV luminosity function
 ~1±1 z~7 galaxy
expected from current
estimates of the luminosity
function (Bouwens et al.
MUV > -20 for typical *
 (Filled Circles = Bouwens
et al. 2007, 2008)
Trends in LF evolution continue beyond z~6
Maintaining an ionized IGM?
 To maintain a completely ionized IGM at z~7 (e.g.
Madau et al. 1999):
 Assumes Salpeter IMF and Solar metallicity
 For C~10, and fesc ~ 0.1 (???), at z~7 this gives
0.13 Msun yr-1 Mpc-3
 Estimate from our data: several times too small
 14.4 arcmin2 of new NICMOS Parallel
fields reveal no z>7 candidates
 Agrees with Bouwens et al. (2008)
tentative z~7 LF
 Future prospects for expanding z~7-10
 WFC3 (PIs Illingworth, Trenti, Yan)

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