Evolution in the properties of Lyman-α emitters from redshifts z ~ 3 to z ~ 2

By K. Nilsson, C. Tapken, P. Moeller, W. Freudling, Johan Peter Uldall Fynbo, K. Meisenheimer, P. Laursen, Goeran Oestlin Mpia Heidelberg, Eso - Garching, D. C. Centre and 1 more. 2008

134 citations recorded by the source corpus.

Context: Narrow-band surveys to detect Lyα emitters are powerful tools for identifying high, and very high, redshift galaxies. Although samples are increasing at redshifts z = 3 {-} 6, the nature of these galaxies is still poorly known. The number of galaxies detected at redshifts below z ˜ 3 are also small. Aims: We study the properties of z = 2.25 Lyα emitters and compare them with those of z > 3 Lyα emitters. Methods: We present narrow-band imaging made with the MPG/ESO 2.2m telescope and the WFI (Wide Field Imager) detector. Using this data, we have searched for emission-line objects. We find 170 candidate typical Lyα emitters and 17 candidates that we regard as high UV-transmission Lyα emitters. We have derived the magnitudes of these objects in 8 photometric bands from u* to K_s, and studied whether they have X-ray and/or radio counterparts. Results: We demonstrate that there has been significant evolution in the properties of Lyα emitters between redshift z ˜ 3 and z = 2.25. The spread in spectral energy distributions (SEDs) at the lower redshift is larger and we detect a significant AGN contribution in the sample. The distribution of the equivalent widths is narrower than at z ˜ 3, with only a few candidates with rest-frame equivalent width above the predicted limit of 240 A. The star formation rates derived from the Lyα emission compared to those derived from the UV emission are lower by on average a factor of ˜ 1.8, indicative of a significant absorption by dust. Conclusions: Lyα emitters at redshift z = 2.25 may be more evolved than Lyα emitters at higher redshift. The red SEDs imply more massive, older and/or dustier galaxies at lower redshift than observed at higher redshifts. The decrease in equivalent widths and star formation rates indicate more quiescent galaxies, with in general less star formation than in higher redshift galaxies. At z = 2.25, AGN appear to be more abundant and also to contribute more to the Lyα emitting population. Full Table 2 is only available in electronic form at http://www.aanda.org

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b03fb5cb8fc638317f9db2c889e2c7471e6a0f3e

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Citations in the corpus

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).”
VERY STRONG EMISSION-LINE GALAXIES IN THE WFC3 INFRARED SPECTROSCOPIC PARALLEL SURVEY AND IMPLICATIONS FOR HIGH-REDSHIFT GALAXIES, (2011, result): “This is consistent with the fraction found in z ∼ 0.3−2 Lyα emitters (Atek et al. 2009; Scarlata et al. 2009; Nilsson et al. 2009; Cowie et al. 2010, 2011), and what is locally found in emission-line galaxy samples (e.g. Hao et al. 2005).”
THE HETDEX PILOT SURVEY. II. THE EVOLUTION OF THE Lyα ESCAPE FRACTION FROM THE ULTRAVIOLET SLOPE AND LUMINOSITY FUNCTION OF 1.9 (2010, methodology): “At z ∼ 2.1, Guaita et al. (2010) measures a mean SFR(Lyα) to SFR(UV ) ratio of 0.66 for narrow-band selected LAEs, consistent with the 0.56 value measured by Nilsson et al. (2009a) at z ∼ 2.3.”
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).”
Lyα-EMITTING GALAXIES AT z = 2.1 IN ECDF-S: BUILDING BLOCKS OF TYPICAL PRESENT-DAY GALAXIES? (2009, methodology): “This characteristic equivalent width is comparable to that measured at z ' 3.1 by Grownwall et al. (2007), w0 = 76 +11 −8 Å, but it is greater than the value measured by Nilsson et al. (2009) at z ' 2.3, w0 = 48.5± 1.7 Å.”
Extended Lyman α haloes around individual high-redshift galaxies revealed by MUSE (2015, background): “…LAEs embedded in largescale extended Lyα emission and presented a first composite Lyα image providing clear evidence of excess flux beyond the PSF. Nilsson et al. (2009) compared the widths of a large sample of z ' 2.2 LAE candidates and noted that they were “generally more extended in the…”
DIFFUSE Lyα EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES (2011, methodology): “We note that the values in Table 3 for fesc,rel have been obtained using a method that appears to differ from that used in some recent work (e.g., Gronwall et al. 2007; Nilsson et al. 2009; Kornei et al. 2010).”
THE COSMOS2015 CATALOG: EXPLORING THE 1 < z < 6 UNIVERSE WITH HALF A MILLION GALAXIES (2016, methodology): “…emission line galaxies at z ∼ 2.2 (Zabl 2015): five of the galaxies have been selected based on [OII]λλ3726, 3729 emission in the VISTA NB118 data (Milvang-Jensen et al. 2013) using previous COSMOS photometric redshift, and one of them through Ly-α emission from the sample of Nilsson et al. (2009).”