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Photometric Properties of Lyα Emitters at z=3.1: Insights from the MUSYC Collaboration

This study delves into the photometric properties of Lyman-alpha emitters (LAEs) at redshift z=3.1, based on a narrow-band survey of E-CDFS yielding 160 LAEs. The research reveals crucial findings on equivalent widths (EWs) and star formation rates (SFRs), showing a low fraction of LAEs with high EWs and an exponential EW distribution. The analysis of deep broadband photometry highlights the UV and Lyα SFRs, with the latter being lower. The findings suggest that these LAEs are low-mass, young galaxies with low dust content, significantly contributing to our understanding of galaxy formation.

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Photometric Properties of Lyα Emitters at z=3.1: Insights from the MUSYC Collaboration

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  1. Photometric Properties of Ly Emitters at z = 3.1 Robin Ciardullo (PSU) Collaborators: Caryl Gronwall (PSU), Eric Gawiser (Rutgers), John Feldmeier (YSU) + the MUSYC collaboration Heidelberg

  2. Photometry • Narrow-band survey of the E-CDFS generated a sample of 160 LAEs with 3.08 < z < 3.12, EW0 > 19.4 Å and L(Lya) > 1.3  1042 ergs-s-1 • Deep broadband photometry from MUSYC allows for detailed exploration of the continuum properties of this sample • 5 mAB limits: U=26.0, B=26.9, V=26.4, R=26.4 • Knowledge of LAE positions allows for fainter photometry beyond completeness limits Heidelberg

  3. Rest Frame Equivalent Widths • Less than 10% of LAEs have EW0 > 240 Å • EW distribution is exponential with scale length of 76  10 Å • Extrapolation implies ~20% of LAEs fall below the EW cutoff • EW distribution agrees with Le Delliou models Heidelberg

  4. Rest Frame Equivalent Widths UV-bright galaxies have (relatively) low Ly equivalent widths No correlation between LyEW and slope of UV continuum Heidelberg

  5. LAE Broadband Colors • LAEs are blue, B-R ~ 0.5 • LAEs are inhomogeneous, B-R > 0.3 (intrinsic) • LAEs usually lie below the limits of LBG identifications Heidelberg

  6. LAE Broadband Colors • LAEs are blue, B-R ~ 0.5 • LAEs are inhomogeneous, B-R > 0.3 (intrinsic) • LAEs usually lie below the limits of LBG identifications • LAEs fall in the same region of color-color space as LBGs (all with 1 of locus) Heidelberg

  7. Implied Star-Formation Rates If we translate the UV continuum to a SFR (via Kennicutt 1998) and the Ly flux to a SFR (via Case B), then UV SFRs are ~ 3 times greater than Ly rates. SFR(Ly): ~ 3 M yr-1 When normalized to mass (talk by Guaita) SFR(Ly)/Mass ~ 4 10-9 Myr-1 M-1 Heidelberg

  8. Extinction (Assuming Calzetti Law) Note: it doesn’t take much dust to make the UV and Ly SFRs agree E(B-V)s < 0.05 Heidelberg

  9. LAE and the Universal SFR Density • Ignore dust for now… • Take LAE Luminosity Function Heidelberg

  10. LAE and the Universal SFR Density • Ignore dust for now… • Take LAE Luminosity Function • Take Schechter parameter likelihoods = 1.49  0.4 L* = 42.6  0.2 T = 1.46  0.14  10-3 Mpc-3 Heidelberg

  11. LAE and the Universal SFR Density • Ignore dust for now… • Take LAE Luminosity Function • Take Schechter parameter likelihoods • Compute likelihoods for SFR density • Most-likely SFR density 6.5  10-3 M yr-1 Mpc-3 • For E(B-V) ~ 0.05, SFRD ~ 0.012 M yr-1 Mpc-3 LBG SFRD is between 0.01 and 0.05 M yr-1 Mpc-3 Heidelberg

  12. Conclusions • LAEs at z ~ 3.1 are young, low-mass, low dust systems -- galaxies in the act of formation, but not Pop III • No extremely high EW LAEs seen • Low amount of inferred dust (also from SED fitting); • Typical SFRs between 1 and 10 M yr-1 • Very high specific star formation rates (from SED fitting) • Two large, new samples in hand: z ~ 2.1 and 3.1 Heidelberg

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