Probing the faint end of the Galaxy luminosity function at $\vec{z}=$ 3 with Lyαemission

Abstract

Abstract. We present spectroscopic observations obtained with the ESO Very Large Telecope (VLT) of seven candidate Lyα emitting galaxies in the field of the radio quiet Q1205-30 at z = 3.04 previously detected with deep narrow band imaging. Based on equivalent widths and limits on line ratios we confirm that all seven objects are Lyα emitting galaxies. Deep images also obtained with the VLT in the B and I bands show that five of the seven galaxies have very faint continuum fluxes (I(AB) ≈ 26.8 and B(AB) ≈ 27.3). The star formation rates of these seven galaxies estimated from the rest-frame UV continuum around 2000Å, as probed by the I-band detections, as well as from the Lyα luminosities, are 1-4 M yr −1 assuming a Hubble constant of 65 km s −1 Mpc −1 , Ωm = 0.3, and ΩΛ = 0.7. This is 1-3 orders of magnitude lower than for other known populations of star-forming galaxies at similar redshifts (the Lyman-Break galaxies and the sub-mm selected sources). The inferred density of the objects is high, 16 ± 4 per arcmin 2 per unit redshift. This is consistent with the integrated luminosity function for Lyman-Break galaxies down to R = 27 if the fraction of Lyα emitting galaxies is ≈70% at the faint end of the luminosity function. However, if this fraction is 20% as reported for the bright end of the luminosity function then the space density in this field is significantly larger (by a factor of 3.5) than expected from the luminosity function for Lyman-Break galaxies in the HDF-North. This would be an indication that at least some radio quiet QSOs at high redshift reside in overdense environments or that the faint end slope of the high redshift luminosity function has been underestimated. We find evidence that the faint Lyα galaxies are essentially dust-free. These observations show that Lyα emission is an efficient method by which to probe the faint end of the luminosity function at high redshifts.

The nature ofz ~ 2.3 Lyman-αemitters

“…The narrow-band, i.e. Lyα emission, is clearly more extended than the broad-band component, as has previously been found for other LAEs at both low redshift (Östlin et al 2009) and at high redshift (Møller & Warren 1998;Fynbo et al 2001;Finkelstein et al 2010). This is further evidence that the high EW in this object is driven by resonant scattering, as the Lyα emission is expected to be more extended than the continuum emission in those cases (Östlin et al 2009).…”

Quasars Clustering atz ≈ 3 on Scales ≲10h−1Mpc

“…Steidel et al (2000) have recently presented strong evidence of a significant concentration of galaxies at z % 3 based on Lyman break color selection. Fynbo, Mö ller, & Thomsen (2001) and Möller & Fynbo (2001) have measured star formation rates on seven Ly -emitting galaxies located in a filament at z % 3, detected with narrowband imaging techniques and confirmed spectroscopically.…”

Evolution in the properties of Lyman-αemitters from redshiftsz~ 3 toz ~ 2

“…The volume density is 0.00062 Mpc −3 , which is in the lower range of that observed at redshift z ∼ 3. Fynbo et al (2001) summarise the surface densities of several early z ∼ 3 surveys. With the exception of the Steidel et al (2000) survey in the overdense SSA22 field, these surveys all determined values of 2.11−5.9 arcmin −2 z −1 to the flux limit of this survey, but with large error bars.…”

“…the broad-band counterparts are consistent with being pure point-sources whereas the narrow-band objects are significantly more extended than point-sources (cf. Møller & Warren 1998;Fynbo et al 2001Fynbo et al , 2003a. This may arise from diffuse scattering of Lyα within the galaxy (see also Laursen & Sommer-Larsen 2007) and/or due to the diffuse ISM (Östlin et al 2008).…”

“…Objects with large equivalent widths (EWs) are thus selected by comparing the colours in the narrow-band image and complementary broad-band images. Spectroscopically confirmed Lyα emitters now include several hundreds of sources at redshifts z ∼ 3 (e.g., Møller & Warren 1993;Cowie & Hu 1998;Steidel et al 2000;Fynbo et al 2001Fynbo et al , 2003aMatsuda et al 2005;Venemans et al 2007;Nilsson et al 2007;Ouchi et al 2008), z ∼ 4.5 (Finkelstein et al 2007), z ∼ 5.7 (Malhotra et al 2005;Shimasaku et al 2006;Tapken et al 2006) and z ∼ 6.5 (Taniguchi et al 2005;Kashikawa et al 2006). However, in the low redshift range, between z ≈ 1.6 corresponding to the atmospheric cut-off in the UV and z ∼ 3, little progress has been made.…”