1. The First Galaxies in the Hubble Frontier Fields Rachana Bhatawdekar, Christopher Conselice The University of Nottingham

2. Introduction  Exploring the very first galaxies is one of the major contemporary problems in astrophysics.  Addressed best with deep imaging observations

4. Frontier Fields?  A HST project to examine six galaxy clusters and six nearby blank fields – Frontier Fields  140 orbits per cluster/blank field pair in 7 photometric bands (spanning 0.4–1.6µm) with ACS and WFC3 for a total of 840 orbits  The 5σ detection limit for point sources is ~ 29th magnitude AB in each filter

5. Locations of the clusters on the sky

6. Motivation  Detect and examine the objects  Subtract the BCGs for a deeper and cleaner detection.  Extraction of physical properties: Luminosity functions, stellar mass functions and star formation rates

7. H-band image of MACS0416 cluster

8. Over subtraction of BCGs in MACS0416

9. GALAPAGOS for subtraction Single Sersic model results in bad residual images Too many neighboring galaxies Method Observed Image Model Residual

10. Divide and Conquer!  Used GALFIT on small regions to fit the small objects first  Simulate galaxy of interest using one or more Sersic models  Subtracted model from the original image

11. 2 Sersic components for small galaxy and 4 for the big galaxy Observed Image Model Residual

12. 9 Sersic components

13. Cluster with massive galaxies

14. Massive galaxies subtracted from the cluster

15. Photometry  PSF matching - Convolved the ACS images (high resolution) with the PSF of H-band (low resolution).  SExtractor for detection of objects.  Detections in original image = 1324  Detection in subtracted image = 1362  SExtractor in dual image mode – subtracted H-band image for detection and photometry in the original H- band image.

16. Colour–magnitude diagram Change in photometry for 5% galaxies after subtraction

17. Selection Criteria  Lyman break technique to select high-redshift objects (Steidel et al. 1996)  Non detection criteria in bands blueward of LB.  Colour selection in bands redward of the break.  Colour Criteria for F814W (z~6) dropouts (Atek et al. 2014): (F814W - F105W) > 0.8 (F814W - F105W) > 0.6 +2 (F105W - F125W) (F105W - F125W) < 0.8

18. 52 drop outs Retained 17 sources as good z~6 candidates

19. Stellar Mass

20. Conclusions and future work  FF BCGS need more than one Sersic component to be modeled correctly.  Stellar mass agrees with previous observations and expectations for objects in the early Universe.  Compute photometric redshifts by fitting photomeric data with SED templates using EAZY (Brammer, van Dokkum & Coppi 2008)  Include Spitzer (IRAC 3.4 and 5.4 microns) data for redshift accuracy.  Calculate mass function, luminosity function etc.  Perform the same analysis on Abell 2744 and MACS J0717.5+3745 cluster.