1. Galaxies at z=6-9 from the WFC3/IR Imaging of the Hubble Ultra Deep Field Presented By Kyle Burns AST 494 March 5, 2009

2. Backround Z- The redshift of an object. Z=∆ /

3. The Story So Far… Difficult to extend observations beyond z=7 Due in part to the continued decline of number density of galaxies at high redshifts. Need for more sensitive near-IR imaging. Enter WFC3!

4. Wide Field Camera 3 167 arcsec X 167 arcsec (2.7 X 2.7 arcmin) field of view. 200-1700 nm of spectral coverage Three filters used for this paper F105W(Y 105 ) F125W(J 125 ) F160W(H 160 ) http://hubblesite.org/the_telescope/nuts_.and._bolts/wavelengths.php

5. Observations Completed over 62 orbits between August 26- September 6, 2009. Cover 4.5arcmin 2 of the 11 arcmin 2 covered by the ACS. Orbits divided between filters 28 Orbits in H 160 16 Orbits in J 125 18 Orbits in Y 160

6. Observations Benefits from the ACS images. Important for determining a strong Lyman break (1215 Å) to greater than 9500 Å. 1400 second exposures.

7. Lyman Break Galaxies Star forming galaxies at z>2.5 Not seen in ultra-violet filters Can be seen in the green, red and nea-IR.

8. Redshift Estimation 300 candidates Observed photometry was fitted with synthetic galaxy templates IRAC data was used to rule out galxies of z=5-6

10. The Sample Of the 300 catalogue objects refined to 49. SED fits and  2 vs. Z for all 49 galaxies. The independent list contains all but the faintest of Oesch et al. and Bouwens et al. Also contains 15 additional galaxies not previously noticed by Oesch at Z>6.25

11. Results 15 Galaxies at z>7 and three at z> Strong clustering in the z  8 galaxies Just one little minor problem…

12. Balmer Break These galaxies can also be z  1.6 Low luminosity at a much lower redshift. Interloper galaxies could also be clustered. “We have yet to uncover a completely compelling example of a galaxy at z>8 in the WFC3/IR image of the HUDF”

13. Discussion When will it be safe to consider these candidates as high redshift galaxies? What is needed for future studies?

14. Luminosity Function

15. Implications for Re-ionization If sources of M=-10 are included; re- ionization would only be completed at z = 4.5 “Difficult for the observed population of star-forming galaxies to achieve re- ionization by z  6 without a significant contribution from galaxies well below the detection limits…”

16. Summary 49 galaxies with z>5.9 Acceptable low redshift solutions for 27 of the 37 at z>6.3 and all z>8. Number density declines by a factor of  2.5 at z=6-7 and by another factor of 2 by z  8.