Ly  Emission-Line Galaxies at z=3.1 in the Extended CDF-S

1. Ly Emission-Line Galaxies at z=3.1 in the Extended CDF-S Caryl Gronwall (PSU) Collaborators: Robin Ciardullo (PSU), Eric Gawiser (Rutgers), John Feldmeier (YSU) + the MUSYC collaboration See Gronwall et al. 2007, ApJ, 667, 70 Gawiser et al. 2007, ApJ, 671, 278

2. Why z ~ 3.1? • Makes use of existing [O III] 5007 filter • Enables direct comparison to z ~ 3 Lyman break galaxies; LAEs dominate the faint end of LF • Can obtain large statistically complete samples • Note at z ~ 4, Ly emitters are as easy to detect as LBGs; at z ~ 6 they are the only galaxies observable from the ground. • Samples at z > 4.4 are contaminated by H • z ~ 3.1 provides an “intermediate” redshift for the population; most current efforts are concentrated on z > 5 • Falls in redshift range planned for HETDEX: 2<z<4 (talk by Blanc) • z ~ 3.1 are the contaminants in narrow-band surveys for intracluster planetary nebulae (Feldmeier, Ciardullo et al.) Heidelberg

3. Our Observations • Narrow-band [O III] 5007 imaging using Mosaic camera on the CTIO 4-m telescope • Region: the Extended Chandra Deep Field South • 32 x 32 region, 0.28 square degrees • 20-hour(!) exposure through the 50 Å FWHM filter • Redshift range 3.08 < z < 3.12 • Off-band derived from deep B + V (~3 hours in each band) images • Detect galaxies via: • Difference image • On-band – Off-band color Heidelberg

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6. On Off Difference Heidelberg

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8. Results • Detected 162 Ly emitters with • EWobs > 80 Å EW0 > 19.4 Å • Flux(Ly) > 1.5 x 10-17 ergs-cm-2-s-1 or L(Ly) > 1.3  1042 ergs-s-1 • This sample is large enough for statistical analysis, allowing us to study the evolution in number density. • 4.6  0.4 per square arcmin per unit z . • Leverages multiwavelength data in this field. Heidelberg

9. Spectroscopic Follow-up Results from Gronwall et al. (2007): 160 LAEs (and 2 AGN) identified: To date, 60 objects have confirmed redshifts. • 98% of LAE candidates are confirmed as Ly emitters • Follow-up spectroscopy of 92 LAEs with Magellan/IMACS • Measurable redshifts from 62/92 objects • One interloper at z=1.6 (via the CIII] 1909 line) • One z=3.1 AGN (with emission from CIV 1550) • Remaining 60 are “normal” LAEs at z=3.1 • No [O II] emitters! Heidelberg

10. Spectroscopic Follow-up Results from Gronwall et al. (2007): 160 LAEs (and 2 AGN) identified: To date, 60 objects have confirmed redshifts. • 98% of LAE candidates are confirmed as Ly emitters • Follow-up spectroscopy of 92 LAEs with Magellan/IMACS • Measurable redshifts from 62/92 objects • One interloper at z=1.6 (via the CIII] 1909 line) • One z=3.1 AGN (with emission from CIV 1550) • Remaining 60 are “normal” LAEs at z=3.1 • No [O II] galaxies! Heidelberg

11. Filter transmission curve Non-square bandpasses require careful modeling!!! • Observed LF is convolution of true LF and the derivative of the inverse of the filter transmission function • Objects on filter wings are subject to equivalent width censoring Result: effective volume of the survey is defined by the filter’s full-width at 2/3-max! Heidelberg

12. Observed and True Ly Luminosity Function Heidelberg

13. Ly Luminosity Function Schechter Parameters • = 1.49  0.4 ; L* = 42.6  0.2 N(> 1.5 x 10-17, EW0 > 19 Å) = 1.46  0.14  10-3 Mpc-3 Heidelberg

14. Evolution of LAE LF Heidelberg

15. Continuum LF compared to LBGs LAEs are ~1/3 the density of LBGs at same redshift. LAE LF extends much fainter, but are censored by equivalent width Heidelberg

16. Multi-wavelength Data • Only 2 LAE candidates are x-ray sources from ECDF-S catalogs. Ly emitters are not high-luminosity AGN (quasars). • Stacking analysis yields Lx < 3.8  1041 ergs-s-1 in the 0.2 - 2 keV band. They are not low luminosity AGN. • Stacking of optical + near-IR + IRAC photometry (Gawiser et al. 2007) places constrainsts on ages, mass, dust, star formation history. (Talk by Guaita) • Available HST data from GOODS/GEMS allows for exploration of continuum morphologies (see also poster by Bond). Heidelberg

17. Multi-wavelength Data • 28 Ly emitters are located within HST/ACS GOODS field, allowing for a detailed study of their morphologies (The entire field is covered by GEMS, providing even more information.) • 10 LAEs are in GOODS catalog • LAEs tend to be small: 0.05 to 0.3 (0.4 - 2.3 kpc), majority are sub-kpc • Many show evidence of merging • Quantitative morphological analysis using GALFIT: majority are highly concentrated, but with a variety of Sersic profiles Heidelberg

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19. Conclusions • LAEs at z~3 are relatively easy to detect. We have a well-defined statistical sample which allows us to study the detailed properties of these galaxies. • Follow-up spectroscopy confirms that these are LAEs. • Little observed evolution in the LFs of LAEs from z ~ 6 to z ~ 3. This implies intrinsic evolution due to IGM absorption. • Leverages multi-wavelength data on this field. • Other results from this sample: • Photometric properties (see talk by Ciardullo) • Morphologies (see poster by Bond) • Clustering (see poster by Francke) • SED fitting (see talk by Guaita) Heidelberg

20. Upcoming Work • Follow-up optical spectroscopy -- in progress using Magellan IMACS + VLT/VIMOS. Also plan to use higher resolution SALT/RSS to resolve the Ly emission line for probe kinematics. • Comparable E-CDFS data for 3.10 < z < 3.14 in hand • Greater volume/greater depth • Spatial correlation function • Comparable data through [O II] filter (z ~ 2.1) in hand • Evolution and LAE properties at lower redshift • Detailed comparison to LBGs at same redshift • Comparison of continuum and Ly morphologies at HST resolution Heidelberg