The Great Escape

1
The Great Escape

• A search for leaking Lyman continuum at z 1.2
• Brian Siana
• Spitzer Science Center
• Deep06

Harry Teplitz, James Colbert (SSC) Henry
Ferguson, Mauro Giavalisco (STScI) Jonathan
Gardner (Goddard), Mark Dickinson (NOAO) GOODS et
al.
2
Reionization

• WMAP ?es --gt Reionization began at z11-14
• QSO Gunn Peterson trough --gt IGM ionized by z6
• What reionized the universe?
• QSOs? Rapid decline in space density at z gt 2.5
• Faint end slope? Probably not sufficient.
  (Inoue et al. 2006, Siana et al. 2006)
• Star-formation
• Escape fraction of ionizing photons? Who knows.
  If fesc gt 0.1
• But what is fesc ?

3
The search
4
Summary of Studies in Literature

• z0 1/6 detections (fesc lt 0.10)
• z1 0/11 detections (fesc lt 0.15)
• z3 2/15 detections
• 2 detections have fesc 1
• ltfescgt 0.15
• Increasing fesc with redshift ?

5
Lots of Questions

• What is special about the galaxies with high
  fesc?
• Is fesc a function of morphology or luminosity?
• Is fesc anisotropic?
• Does fesc evolve with redshift?
• Pop III stars (Jimenez Haiman, 2006)
• Increased SF efficiency --gt SNe Chimneys (Fujita
  et al. 2004)
• Gas clumping/feedback (Razoumov et al. 2006)
• We have not sampled enough morphology/L/z space!

6
The Survey

• HST ACS-Solar Blind Channel - 1600Å photometry
• 12 arcmin2 in covering HDF-N and UDF
• Blueward of Lyman Break at z gt 1.2
• mAB(1600Å) lt 29
• 29 gals with 1.2ltzspeclt1.5
• We can triple z1 sample size and sample low L
  space

B
FUV
7
A Difficult Measurement
?(f1500/f700)
FUV
1500Å
Intrinsic
Dust E(B-V)0.2
IGM
8
Method

• Measure (f1500/f700)obs
• Assumptions
• (f1500/f700)int 8
• exp(?IGM) 2.5
• No differential dust reddening

9
B
FUV
10
Results

• 15 galaxies
• fesc(3?) lt 1
• E(B-V) lt 0.4 (like LBGs)
• No indication of anything like leaking z3 LBGs
  (Shapley et al. 2006)
• Stack fesc(3?) lt 11
• However

11
Caveat

• Many assumptions required
• No differential reddening between 700-1500Å
• Small intrinsic Lyman Break associated with young
  systems.
• We can fit SED --gt dust reddening, age
• Can result in 3-10 decrease in fesc limits.

12
f1500/f700 gt 106 fesclt 0.15
B
FUV
U
B
V
I
J
H
13
f1500/f700 gt 130 fesclt 0.16
14
Conclusions

• When calculated as usual
• 15 gals with fesc lt 1
• Stacked fesclt 0.11
• Indicates possible evolution in fesc with z
• When fitting for age and reddening
• 2 gals with fesc lt 1
• Stacked fesc lt 0.48
• Need deeper data for definitive proof of fesc
  evolution

15
Stay tuned

• 75 orbits of HST ACS/SBC Imaging (H. Teplitz, PI)
• 15 B23, B-Vlt 0.2 gals in GOODS
• 5 orbits/galaxy
• Placed on low dark current portion of detector
• Observations spaced out to keep detector cool --gt
  low dark current
• gt 10x more sensitive than current survey
• 10 more serendipitous z1 gals in FOV
• Conclusive determination of fesc evolution
  between 1ltzlt3
• Investigate where escape occurs if at all
• Observed 3 galaxies two weeks ago.
• SBC currently turned off. ( ( (

16
contributions to f1500/f700
17
Benefits of Ancillary Data

• Optimize extraction using optical (B band)
  isophotes.
• Determine where Lyman continuum is escaping.
• Great HST photometry for SED fitting.

18
HDF-N

• ACS/SBC 1600Å
• 14 pointings x 2 orbits
• m(AB) lt 29
• 3.77 arcmin2

19
Ultra Deep Field

• ACS/SBC 1600Å
• 25 pointings x 2 orbits
• m(AB) lt 28.5
• 7.77 arcmin2

20
HDF-N Closeup
B
FUV
21
Summary

• Our survey 15 gals _at_ z1.2 with fesc lt 1
• Malkan et al. (2003) 11 gals _at_ z1.2 with fesc
  lt 0.1
• Has something changed between z3 and z1 ?
• Not quite. We have the photometry to predict
  the effect of dust and starburst age on f1500/f700