| 1. |
- de La Vieuville, G., et al.
(författare)
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Faint end of the z similar to 3-7 luminosity function of Lyman-alpha emitters behind lensing clusters observed with MUSE
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 628
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Tidskriftsartikel (refereegranskat)abstract
- Contact. This paper presents the results obtained with the Multi-Unit Spectroscopic Explorer (MUSE) at the ESOVery Large Telescope on the faint end of the Lyman-alpha luminosity function (LF) based on deep observations of four lensing clusters. The goal of our project is to set strong constraints on the relative contribution of the Lyman-alpha emitter (LAE) population to cosmic reionization.Aims. The precise aim of the present study is to further constrain the abundance of LAEs by taking advantage of the magnification provided by lensing clusters to build a blindly selected sample of galaxies which is less biased than current blank field samples in redshift and luminosity. By construction, this sample of LAEs is complementary to those built from deep blank fields, whether observed by MUSE or by other facilities, and makes it possible to determine the shape of the LF at fainter levels, as well as its evolution with redshift.Methods. We selected a sample of 156 LAEs with redshifts between 2.9 <= z <= 6.7 and magnification-corrected luminosities in the range 39 less than or similar to log L-Ly alpha [erg s(-1)] less than or similar to 43. To properly take into account the individual differences in detection conditions between the LAEs when computing the LF, including lensing configurations, and spatial and spectral morphologies, the non-parametric 1/V-max method was adopted. The price to pay to benefit from magnification is a reduction of the effective volume of the survey, together with a more complex analysis procedure to properly determine the effective volume V-max for each galaxy. In this paper we present a complete procedure for the determination of the LF based on IFU detections in lensing clusters. This procedure, including some new methods for masking, effective volume integration and (individual) completeness determinations, has been fully automated when possible, and it can be easily generalized to the analysis of IFU observations in blank fields.Results. As a result of this analysis, the Lyman-alpha LF has been obtained in four different redshift bins: 2.9 < z < 6; 7, 2.9 < z < 4.0, 4 : 0 < z < 5.0; and 5 : 0 < z < 6.7 with constraints down to log L-Ly alpha = 40.5. From our data only, no significant evolution of LF mean slope can be found. When performing a Schechter analysis also including data from the literature to complete the present sample towards the brightest luminosities, a steep faint end slope was measured varying from alpha = -1.69(-0.08)(+0.08) to alpha = -1.87(-0 .12)(+0.12) between the lowest and the highest redshift bins.Conclusions. The contribution of the LAE population to the star formation rate density at z similar to 6 is less than or similar to 50% depending on the luminosity limit considered, which is of the same order as the Lyman-break galaxy (LBG) contribution. The evolution of the LAE contribution with redshift depends on the assumed escape fraction of Lyman-alpha photons, and appears to slightly increase with increasing redshift when this fraction is conservatively set to one. Depending on the intersection between the LAE/LBG populations, the contribution of the observed galaxies to the ionizing flux may suffice to keep the universe ionized at z similar to 6.
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| 2. |
- Thai, T. T., et al.
(författare)
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Probing the faint-end luminosity function of Lyman-alpha emitters at 3 < z < 7 behind 17 MUSE lensing clusters
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 678
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Tidskriftsartikel (refereegranskat)abstract
- Context. This paper presents a study of the galaxy Lyman-alpha luminosity function (LF) using a large sample of 17 lensing clusters observed by the Multi Unit Spectroscopic Explorer (MUSE) at the ESO Very Large Telescope (VLT). The magnification resulting from strong gravitational lensing by clusters of galaxies and MUSE spectroscopic capabilities allows for blind detections of LAEs without any photometric pre-selection, reaching the faint luminosity regime.Aims. The present work aims to constrain the abundance of Lyman-alpha emitters (LAEs) and quantify their contribution to the total cosmic reionization budget.Methods. We selected 600 lensed LAEs behind these clusters in the redshift range of 2.9 < z < 6.7, covering four orders of magnitude in magnification-corrected Ly-α luminosity (39.0 < log(L)[erg s−1] < 43.0). These data were collected behind lensing clusters, indicating an increased complexity in the computation of the LF to properly account for magnification and dilution effects. We applied a non-parametric Vmax method to compute the LF to carefully determine the survey volume where an individual source could have been detected. The method used in this work follows the recipes originally developed in previous works, with some improvements to better account for the effects of lensing when computing the effective volume.Results. The total co-moving volume at 2.9 < z < 6.7 in the present survey is ∼50 103 Mpc3. Our LF points in the bright end (log(L) [erg s−1] > 42) are consistent with those obtained from blank field observations. In the faint luminosity regime, the density of sources is well described by a steep slope, α ∼ −2 for the global redshift range. Up to log(L) [erg s−1] ∼ 41, the steepening of the faint end slope with redshift, suggested in earlier works, is observed, but the uncertainties are still large. A significant flattening is observed towards the faintest end, for the highest redshift bins, namely, log(L)[erg s−1] < 41.Conclusions. When taken at face value, the steep slope at the faint-end causes the star formation rate density (SFRD) to dramatically increase with redshift, implying that LAEs could play a major role in the process of cosmic reionization. The flattening observed towards the faint end for the highest redshift bins still requires further investigation. This turnover is similar to the one observed for the UV LF at z ≥ 6 in lensing clusters, with the same conclusions regarding the reliability of current results. Improving the statistical significance of the sample in this low-luminosity high-redshift regime is a difficult endeavour that may lead to potentially valuable leads in understanding the process of reionization.
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| 3. |
- Goovaerts, I., et al.
(författare)
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Evolution of the Lyman-α-emitting fraction and UV properties of lensed star-forming galaxies in the range 2.9 < z < 6.7
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 678
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Tidskriftsartikel (refereegranskat)abstract
- Context. Faint galaxies are theorised to have played a major role, perhaps the dominant role, in reionising the Universe. Their properties, as well as the Lyman-α emitter (LAE) fraction, XLAE, could provide useful insights into this epoch.Aims. We used four clusters of galaxies from the Lensed Lyman-alpha MUSE Arcs Sample (LLAMAS) that also have deep HST photometry to select a population of intrinsically faint Lyman break galaxies (LBGs) and LAEs. We study the interrelation between these two populations, their properties, and the fraction of LBGs that display Lyman-α emission.Methods. The use of lensing clusters allows us to access an intrinsically faint population of galaxies, the largest such sample collected for this purpose: 263 LAEs and 972 LBGs with redshifts between 2.9 and 6.7, Lyman-α luminosities in the range 39.5 ≲ log(LLyα)(erg s−1)≲42, and absolute UV magnitudes in the range −22 ≲ M1500 ≲ −12. In addition to matching LAEs and LBGs, we define an LAE+continuum sample for the LAEs that match with a continuum object that is not selected as an LBG. Additionally, with the use of MUSE integral field spectroscopy, we detect a population of LAEs completely undetected in the continuum.Results. We find a redshift evolution of XLAE in line with literature results, with diminished values above z = 6. In line with past studies, we take this as signifying an increasingly neutral intervening intergalactic medium. When inspecting this redshift evolution with different limits on EWLyα and M1500, we find that the XLAE for the UV-brighter half of our sample is higher than the XLAE for the UV-fainter half, a difference that increases at higher redshifts. This is a surprising result and can be interpreted as the presence of a population of low Lyman-α equivalent width (EWLyα), UV-bright galaxies situated in reionised bubbles and overdensities. This result is especially interesting in the context of similar, UV-bright, low EWLyα objects recently detected during and around the epoch of reionisation. For intrinsically fainter objects, we confirm the previously observed trend of LAEs among LBGs as galaxies with high star formation rates and low dust content, as well as the trend of the strongest LAEs having, in general, fainter M1500 and steeper UV slopes.
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