We report on the detailed analysis of a gravitationally lensed Y-band dropout, A2744_YD4, selected from deep Hubble Space Telescope imaging in the Frontier Field cluster Abell 2744. Band 7 ...observations with the Atacama Large Millimeter/submillimeter Array (ALMA) indicate the proximate detection of a significant 1 mm continuum flux suggesting the presence of dust for a star-forming galaxy with a photometric redshift of . Deep X-SHOOTER spectra confirms the high-redshift identity of A2744_YD4 via the detection of Ly emission at a redshift z = 8.38. The association with the ALMA detection is confirmed by the presence of O iii 88 m emission at the same redshift. Although both emission features are only significant at the 4 level, we argue their joint detection and the positional coincidence with a high-redshift dropout in the Hubble Space Telescope images confirms the physical association. Analysis of the available photometric data and the modest gravitational magnification ( ) indicates A2744_YD4 has a stellar mass of ∼2 × 109 , a star formation rate of ∼20 yr−1 and a dust mass of ∼6 × 106 . We discuss the implications of the formation of such a dust mass only after the onset of cosmic reionization.
Context. This paper presents the results obtained with the Multi Unit Spectroscopic Explorer (MUSE) for the core of the lensing cluster Abell 1689, as part of MUSE’s commissioning at the ESO Very ...Large Telescope. Aims. Integral-field observations with MUSE provide a unique view of the central 1 × 1 arcmin2 region at intermediate spectral resolution in the visible domain, allowing us to conduct a complete census of both cluster galaxies and lensed background sources. Methods. We performed a spectroscopic analysis of all sources found in the MUSE data cube. Two hundred and eighty-two objects were systematically extracted from the cube based on a guided-and-manual approach. We also tested three different tools for the automated detection and extraction of line emitters. Cluster galaxies and lensed sources were identified based on their spectral features. We investigated the multiple-image configuration for all known sources in the field. Results. Previous to our survey, 28 different lensed galaxies displaying 46 multiple images were known in the MUSE field of view, most of them were detected through photometric redshifts and lensing considerations. Of these, we spectroscopically confirm 12 images based on their emission lines, corresponding to 7 different lensed galaxies between z = 0.95 and 5.0. In addition, 14 new galaxies have been spectroscopically identified in this area thanks to MUSE data, with redshifts ranging between 0.8 and 6.2. All background sources detected within the MUSE field of view correspond to multiple-imaged systems lensed by A1689. Seventeen sources in total are found at z ≥ 3 based on their Lyman-α emission, with Lyman-α luminosities ranging between 40.5 ≲ log (Lyα) ≲ 42.5 after correction for magnification. This sample is particularly sensitive to the slope of the luminosity function toward the faintest end. The density of sources obtained in this survey is consistent with a steep value of α ≤ −1.5, although this result still needs further investigation. Conclusions. These results illustrate the efficiency of MUSE in characterizing lensing clusters on one hand and in studying faint and distant populations of galaxies on the other hand. In particular, our current survey of lensing clusters is expected to provide a unique census of sources responsible for the reionization in a representative volume at z ~ 4−7.
We present the Galaxy Stellar Mass Function (GSMF) up to z~1 from the zCOSMOS-bright 10k spectroscopic sample. We investigate the total MF and the contribution of ETGs and LTGs, defined by broad-band ...SED, morphology, spectral properties or star formation activities. We unveil a galaxy bimodality in the global MF, at least up to the z~0.55, better represented by 2 Schechter functions dominated by ETGs and LTGs, respectively. For the global population we confirm that low-mass galaxies number density increases later and faster than for massive galaxies. We find that the MF evolution at intermediate-low Mstar (logM<10.6) is mostly explained by a growth in stellar mass driven by smooth and decreasing SFHs. The low/negligible evolution at higher Mstar sets a limit of 30-15%, decreasing with redshift, to the fraction of major merging. We find that ETGs increase in number density with cosmic time faster for decreasing Mstar, with a median "building redshift" increasing with mass, in contrast with hierarchical model predictions. For LTGs we find that the number density of blue or spiral galaxies remains almost constant with cosmic time from z~1. Instead, the most extreme population of active star forming galaxies is rapidly decreasing in number density. We suggest, firstly, a transformation from blue active spiral galaxies of intermediate mass into blue quiescent and successively (1-2 Gyr after) into red passive types. The complete morphological transformation into red spheroidal galaxies, required longer time-scales or follows after 1-2 Gyr. A continuous replacement of blue galaxies is expected by low-mass active spirals growing in stellar mass. We estimate that on average ~25% of blue galaxies is transforming into red per Gyr for logM<11. We expect a negligible evolution of the global Galaxy Baryonic MF. ABRIDGED
We describe Hubble Space Telescope (HST) imaging of 10 of the 20 ESO Distant Cluster Survey (EDisCS) fields. Each similar to 40 arcmin super(2) field was imaged in the F814W filter with the Advanced ...Camera for Surveys Wide Field Camera. Based on these data, we present visual morphological classifications for the similar to 920 sources per field that are brighter than l sub(auto)= 23 mag. We use these classifications to quantify the morphological content of 10 intermediate-redshift (0.5 < z < 0.8) galaxy clusters within the HST survey region. The EDisCS results, combined with previously published data from seven higher redshift clusters, show no statistically significant evidence for evolution in the mean fractions of elliptical, S0, and late-type (Sp+Irr) galaxies in clusters over the redshift range 0.5 < z < 1.2. In contrast, existing studies of lower redshift clusters have revealed a factor of similar to 2 increase in the typical S0 fraction between z = 0.4 and 0, accompanied by a commensurate decrease in the Sp+Irr fraction and no evolution in the elliptical fraction. The EDisCS clusters demonstrate that cluster morphological fractions plateau beyond z approximately 0.4. They also exhibit a mild correlation between morphological content and cluster velocity dispersion, highlighting the importance of careful sample selection in evaluating evolution. We discuss these findings in the context of a recently proposed scenario in which the fractions of passive (E, S0) and star-forming (Sp, Irr) galaxies are determined primarily by the growth history of clusters.
We report the discovery of PHz G95.5−61.6, a complex structure detected in emission in the Planck all-sky survey that corresponds to two over-densities of high-redshift (i.e. z> 1) galaxies. This is ...the first source from the Planck catalogue of high-z candidates (proto-clusters and lensed systems) that has been completely characterised with follow-up observations from the optical to the sub-millimetre (sub-mm) domain. Herschel/SPIRE observations at 250, 350, and 500 μm reveal the existence of five sources producing a 500 μm emission excess that spatially corresponds to the candidate proto-clusters discovered by Planck. Further observations at the Canada-France-Hawaii Telescope in the optical bands (g and i) with MegaCam, and in the near infrared (NIR) (J, H and Ks), with WIRCam, plus mid-infrared observations with IRAC/Spitzer (at 3.6 and 4.5 μm), confirm that the sub-mm red excess is associated with an over-density of colour-selected galaxies (i − Ks ~ 2.3 and J − K ~ 0.8 AB-mag). Follow-up spectroscopy of 13 galaxies with VLT/X-Shooter establishes the existence of two high-z structures: one at z ≃ 1.7 (three confirmed member galaxies), the other at z ≃ 2.0 (six confirmed members). The spectroscopic members of each substructure occupy a circular region of comoving radius that is smaller than 1 Mpc, which supports the existence of a physical bond among them. This double structure is also seen in the photometric redshift analysis of a sample of 127 galaxies located inside a circular region of 1′-radius. This contains the five Herschel/SPIRE sources, where we found a double-peaked excess of galaxies at z ≃ 1.7 and z ≃ 2.0 with respect to the surrounding region. These results suggest that PHz G95.5−61.6 corresponds to two accreting nodes, not physically linked to one another, embedded in the large scale structure of the Universe at z ~ 2 and along the same line-of-sight. In conclusion, the data, methods and results illustrated in this pilot project confirm that Planck data can be used to detect the emission from clustered, dusty star-forming galaxies at high z, and, thus, to pierce through the early growth of cluster-scale structures.
During our Herschel Lensing Survey (HLS) of massive galaxy clusters, we have discovered an exceptionally bright source behind the z = 0.22 cluster Abell 773, which appears to be a strongly lensed ...submillimeter galaxy (SMG) at z = 5.2429. This source is unusual compared to most other lensed sources discovered by Herschel so far, because of its higher submm flux (~200 mJy at 500 μm) and its high redshift. The dominant lens is a foreground z = 0.63 galaxy, not the cluster itself. The source has a far-infrared (FIR) luminosity of LFIR = 1.1 × 1014/μ L , where μ is the magnification factor, likely ~11. We report here the redshift identification through CO lines with the IRAM-30 m, and the analysis of the gas excitation, based on CO(7-6), CO(6-5), CO(5-4) detected at IRAM and the CO(2-1) at the EVLA. All lines decompose into a wide and strong red component, and a narrower and weaker blue component, 540 km s-1 apart. Assuming the ultraluminous galaxy (ULIRG) CO-to-H2 conversion ratio, the H2 mass is 5.8 × 1011/μ M , of which one third is in a cool component. From the C I(3P2-3P1) line we derive a C I/H2 number abundance of 6 × 10-5 similar to that in other ULIRGs. The H2Op(2,0,2-1,1,1) line is strong only in the red velocity component, with an intensity ratio I(H2O)/I(CO) ~ 0.5, suggesting a strong local FIR radiation field, possibly from an active nucleus (AGN) component. We detect the NII205 μm line for the first time at high-z. It shows comparable blue and red components, with a strikingly broad blue one, suggesting strong ionized gas flows.
Contact. This paper presents the results obtained with the Multi-Unit Spectroscopic Explorer (MUSE) at the ESO Very 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 ≲ log LLyα erg s−1 ≲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/Vmax 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 Vmax 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 LLyα = 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 α = −1.69−0.08+0.08 α = − 1 . 69 − 0.08 + 0.08 $ \alpha = -1.69^{+0.08}_{-0.08} $ to α = −1.87−0.12+0.12 α = − 1 . 87 − 0.12 + 0.12 $ \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 ∼ 6 is ≲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 ∼ 6.
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
V
max
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 10
3
Mpc
3
. 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.
Observations of distant supernovae indicate that the Universe is now in a phase of accelerated expansion the physical cause of which is a mystery. Formally, this requires the inclusion of a term ...acting as a negative pressure in the equations of cosmic expansion, accounting for about 75 per cent of the total energy density in the Universe. The simplest option for this 'dark energy' corresponds to a 'cosmological constant', perhaps related to the quantum vacuum energy. Physically viable alternatives invoke either the presence of a scalar field with an evolving equation of state, or extensions of general relativity involving higher-order curvature terms or extra dimensions. Although they produce similar expansion rates, different models predict measurable differences in the growth rate of large-scale structure with cosmic time. A fingerprint of this growth is provided by coherent galaxy motions, which introduce a radial anisotropy in the clustering pattern reconstructed by galaxy redshift surveys. Here we report a measurement of this effect at a redshift of 0.8. Using a new survey of more than 10,000 faint galaxies, we measure the anisotropy parameter = 0.70 ± 0.26, which corresponds to a growth rate of structure at that time of f = 0.91 ± 0.36. This is consistent with the standard cosmological-constant model with low matter density and flat geometry, although the error bars are still too large to distinguish among alternative origins for the accelerated expansion. The correct origin could be determined with a further factor-of-ten increase in the sampled volume at similar redshift.
We present an analysis of the stellar mass growth over the last 10 Gyr ($z\le 2$) using a unique large sample of galaxies selected at $3.6~\mu$m. We have assembled accurate photometric and ...spectroscopic redshifts for ~21 200 and 1500 galaxies, respectively, with F(3.6 μm) ≥ 9.0 μJy by combining data from Spitzer-SWIRE IRAC, the VIMOS VLT Deep Survey (VVDS), UKIDSS and very deep optical CFHTLS photometry. We split our sample into quiescent (red) and active (blue) galaxies on the basis of an SED fitting procedure that we have compared with the strong rest-frame color bimodality $(NUV-r')_{\rm ABS}$. The present sample contains ~ 4400 quiescent galaxies. Our measurements of the K-rest frame luminosity function and luminosity density evolution support the idea that a large fraction of galaxies is already assembled at z ~ 1.2, with almost 80% and 50% of the active and quiescent populations already in place, respectively. Based on the analysis of the evolution of the stellar mass-to-light ratio (in K-band) for the spectroscopic sub-sample, we derive the stellar mass density for the entire sample. We find that the global evolution of the stellar mass density is well reproduced by the star formation rate derived from UV based measurements when an appropriate dust correction is applied, which supports the idea of an initial mass function that is on average universal. Over the last 8 Gyr (z ≤ 1.2) we observe that the stellar mass density of the active population shows a modest mass growth rate ($\dot{\rho}$ ~ 0.005(±0.005) $M_{\odot}$/Mpc3/yr), consistent with a constant stellar mass density, $\rho_{\star}^{\rm active}$ ~ 3.1 $\times$ 108 $M_{\odot}$/Mpc3. In contrast, an increase by a factor of ~2 for the quiescent population over the same timescale is observed. As a consequence, the growth of the stellar mass in the quiescent population must be due to the shutoff of star formation in active galaxies that migrate into the quiescent population. We estimate this stellar mass flux to be $\dot{\rho}_{A\rightarrow Q}$ ~ 0.017(±0.004) $M_{\odot}$/Mpc3/yr, which balances the major fraction of new stars born according to our best SFR estimate ($\dot{\rho}$ = 0.025(±0.003) $M_{\odot}$/Mpc3/yr). From $z = 2$ to $z = 1.2$, we observe a major build-up of the quiescent population with an increase by a factor of ~10 in stellar mass (a mass growth rate of ~ 0.063 $M_{\odot}$/Mpc3/yr). This rapid evolution suggests that we are observing the epoch when, for the first time in the history of the universe, an increasing fraction of galaxies end their star formation activity and start to build up the red sequence.
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