Lyα-EMITTING GALAXIES AT z = 2.1 IN ECDF-S: BUILDING BLOCKS OF TYPICAL PRESENT-DAY GALAXIES?

By L. Guaita, E. Gawiser, N. Padilla, H. Francke, Nicholas A. Bond, C. Gronwall, R. Ciardullo, J. Feldmeier, Shawn Sinawa, G. Blanc and 1 more. 2009

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We discovered a sample of 250 Lyα emitting (LAE) galaxies at z ≃ 2.1 in an ultra-deep 3727 Å narrow-band MUSYC image of the Extended Chandra Deep Field-South. The LAEs were selected to have rest-frame equivalent widths (EWs) >20 Å and emission-line fluxes FLyα>2.0 × 10−17 erg cm−2 s−1, after carefully subtracting the continuum contributions from narrow-band photometry. The median emission-line flux of our sample is FLyα = 4.2 × 10−17 erg cm−2 s−1, corresponding to a median Lyα luminosity LLyα = 1.3 × 1042 erg s−1 at z ≃ 2.1. At this flux, our sample is ⩾90% complete. Approximately 4% of the original NB-selected candidates were detected in X-rays by Chandra, and 7% were detected in the rest-frame far-UV by the Galaxy Evolution Explorer; these objects were eliminated to minimize contamination by active galactic nuclei and low-redshift galaxies. At LLyα ⩾ 1.3 × 1042 erg s−1, the EW distribution is unbiased and is represented by an exponential with scale-length 83 ±10 Å. Above this same luminosity threshold, we find a number density of 1.5 ± 0.5 × 10−3 Mpc−3. Neither the number density of LAEs nor the scale-length of their EW distribution show significant evolution from z ≃ 3 to z ≃ 2. We used the rest-frame UV luminosity to estimate a median star formation rate of 4 M☉ yr−1. The median rest-frame UV slope, parameterized by the color B − R, is typical of dust-free, 0.5–1 Gyr old or moderately dusty, 300–500 Myr old population. Approximately 30% of our sample is consistent with being very young (age <100 Myr) galaxies without dust. Approximately 40% of the sample occupies the z ∼ 2 star-forming galaxy locus in the UVR two-color diagram, but the true percentage could be significantly higher taking into account photometric errors. Clustering analysis reveals that LAEs at z ≃ 2.1 have r0 = 4.8 ± 0.9 Mpc, corresponding to a bias factor b = 1.8 ± 0.3. This implies that z ≃ 2.1 LAEs reside in dark matter halos with median masses log(M/M☉) = 11.5+0.4−0.5, which are among the lowest mass halos yet probed at this redshift. We used the Sheth and Tormen conditional mass function to study the descendants of these LAEs and found that their typical present-day descendants are local galaxies with L* properties, like the Milky Way.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

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In Astronomy and Astrophysics

1. M. Ouchi
2. P. Hopkins
3. L. Hernquist
4. J. Dunlop
5. Richard S. Ellis
6. Yoshiaki Ono
7. R. McLure
8. K. Shimasaku

In Nuclear and High Energy Physics

1. M. Ouchi
2. Yoshiaki Ono
3. J. Dunlop
4. R. McLure
5. K. Shimasaku
6. C. Simpson
7. D. Schneider
8. M. Oguri

Citations in the corpus

• SILVERRUSH. IV. Lyα luminosity functions at z = 5.7 and 6.6 studied with ∼1300 Lyα emitters on the 14–21 deg2 sky (2017, background): “…Matsuda et al. 2004; Taniguchi et al. 2005; Iye et al. 2006; Kashikawa et al. 2006; Shimasaku et al. 2006; Gronwall et al. 2007; Murayama et al. 2007; Guaita et al. 2010; Shibuya et al. 2012; Yamada et al. 2012; Konno et al. 2014) and spectroscopic observations (e.g., Deharveng et al. 2008; Adams…”
• Using Lyman-α to detect galaxies that leak Lyman continuum (2014, background): “…huge amount of spectroscopic data are available in Lyα, up to the reionisation redshift (e.g. Shapley et al. 2003; Hu et al. 2010; Stark et al. 2010; Guaita et al. 2010, 2011; Dressler et al. 2011; Bielby et al. 2011; Pentericci et al. 2010, 2011; Kulas et al. 2012; Jiang et al. 2013b,a; Ellis et…”
• STELLAR POPULATIONS OF Lyα EMITTERS AT z ∼ 6–7: CONSTRAINTS ON THE ESCAPE FRACTION OF IONIZING PHOTONS FROM GALAXY BUILDING BLOCKS (2010, background): “2003; Malhotra & Rhoads 2004; Taniguchi et al. 2005; Kashikawa et al. 2006; Shimasaku et al. 2006; Dawson et al. 2007; Gronwall et al. 2007; Murayama et al. 2007; Ouchi et al. 2008; Shioya et al. 2009; Nilsson et al. 2009; Guaita et al. 2010; Hayes et al. 2010).”
• ON THE REDSHIFT EVOLUTION OF THE Lyα ESCAPE FRACTION AND THE DUST CONTENT OF GALAXIES (2010, background): “Third, it is well-known that in individual Lyα-selected systems at redshifts 2–3, the SFR inferred by comparing Lyα and UV radiation is frequently found to be comparable (Guaita et al. 2010; Nilsson et al. 2009; Ouchi et al. 2008).”
• THE HETDEX PILOT SURVEY. II. THE EVOLUTION OF THE Lyα ESCAPE FRACTION FROM THE ULTRAVIOLET SLOPE AND LUMINOSITY FUNCTION OF 1.9 (2010, methodology): “• The star-formation properties (SFR), the Lyα escape fraction in LAEs, and its evo- lution with redshift.”
• STATISTICS OF 207 Lyα EMITTERS AT A REDSHIFT NEAR 7: CONSTRAINTS ON REIONIZATION AND GALAXY FORMATION MODELS (2010, background): “Gawiser et al. (2007) and Guaita et al. (2010) estimate r0 to be 2.5 +0.6 −0.7 h −1 100 Mpc at z = 3.1 and 3.4±0.6 h−1100 Mpc at z = 2.1, respectively, where r0 is converted to values in units of h−1100 Mpc.”