Aims. We wish to investigate the physical properties of a sample of Lyα emitting galaxies in the VANDELS survey, with particular focus on the role of kinematics and neutral hydrogen column density in ...the escape and spatial distribution of Lyα photons. Methods. From all the Lyα emitting galaxies in the VANDELS Data Release 2 at 3.5 z 4.5, we select a sample of 52 galaxies which also have a precise systemic redshift determination from at least one nebular emission line (HeII or CIII). For these galaxies, we derive different physical properties (stellar mass, age, dust extinction and star formation rate) from spectral energy distribution (SED) fitting of the exquisite multi-wavelength photometry available in the VANDELS fields, using a state-of-the-art spectral modeling tool, BEAGLE and the UV β slope from the observed photometry. We characterize the Lyα emission in terms of kinematics, EW, FWHM and spatial extension and then estimate the velocity of the neutral outflowing gas. Thanks to the ultra-deep VANDELS spectra (up to 80 hours on-source integration) this can be achieved for individual galaxies, without relying on stacks. We then investigate the correlations between the Lyα properties and the other measured properties, to study how they affect the shape and intensity of Lyα emission. Results. We reproduce some of the well known correlations between Lyα EW and stellar mass, dust extinction and UV β slope, in the sense that the emission line appears brighter in lower mass, less dusty and bluer galaxies. We do not find any correlation with the SED-derived star formation rate, while we find that galaxies with brighter Lyα tend to be more compact both in UV and in Lyα. Our data reveal a new interesting correlation between the Lyα velocity and the offset of the inter-stellar absorption lines with respect to the systemic redshift, in the sense that galaxies with larger inter-stellar medium (ISM) out-flow velocities show smaller Lyα velocity shifts. We interpret this relation in the context of the shell-model scenario, where the velocity of the ISM and the HI column density contribute together in determining the Lyα kinematics. In support to our interpretation, we observe that galaxies with high HI column densities have much more extended Lyα spatial profiles, a sign of increased scattering. However, we do not find any evidence that the HI column density is related to any other physical properties of the galaxies, although this might be due in part to the limited range of parameters that our sample spans.
We report a search for z {approx} 6.96 Ly{alpha} emitters (LAEs) using a narrowband filter, centered at 9680 A with the Inamori-Magellan Area Camera and Spectrograph instrument on the Magellan ...telescope at Las Campanas Observatory. We obtain a sample of six LAE candidates of luminosity {approx}10{sup 42} erg s{sup -1} in a total area of 465 arcmin{sup 2} corresponding to a comoving volume of {approx}72,000 Mpc{sup 3}. From this result, we derive a Ly{alpha} luminosity function (LF) at z {approx} 6.96 and compare our sample with the only z {approx} 6.96 LAE spectroscopically confirmed to date. We find no evolution between the z = 5.7 and z {approx} 7 Ly{alpha} LFs if a majority of our candidates are confirmed. Spectroscopic confirmation for this sample will enable more robust conclusions.
We present the discovery of a candidate of giant radio-quiet Lyα blob (RQLAB) in a large-scale structure around a high-redshift radio galaxy (HzRG) lying in a giant Lyα halo B3 J2330+3927 at redshift ...z= 3.087. We obtained narrow- and broad-band imaging around B3 J2330+3927 with Subaru/Suprime-Cam to search for Lyα emitters (LAEs) and absorbers (LAAs) at redshift z= 3.09 ± 0.03. We detected candidate 127 LAEs and 26 LAAs in the field of view of 31 × 24 arcmin2 (58 × 44 comoving Mpc). We found that B3 J2330+3927 is surrounded by a 130 kpc Lyα halo and a large-scale (∼60 × 20 comoving Mpc) filamentary structure. The large-scale structure contains one prominent local density peak with an overdensity of greater than 5, which is 8 arcmin (15 comoving Mpc) away from B3 J2330+3927. In this peak, we discovered a candidate 100 kpc RQLAB. The existence of both types of Lyα nebulae in the same large-scale structure suggests that giant Lyα nebulae need special large-scale environments to form. On smaller scales, however, the location of B3 J2330+3927 is not a significant local density peak in this structure, in contrast to the RQLAB. There are two possible interpretations of the difference of the local environments of these two Lyα nebulae. First, RQLAB may need a prominent (δ∼ 5) density peak of galaxies to form through intense starbursts due to frequent galaxy interactions/mergers and/or continuous gas accretion in an overdense environment. On the other hand, Lyα halo around HzRG may not always need a prominent density peak to form if the surrounding Lyα halo is mainly powered by its radio and active galactic nucleus activities. Alternatively, both RQLAB and Lyα halo around HzRG may need prominent density peaks to form but we could not completely trace the density of galaxies because we missed evolved and dusty galaxies in this survey.
ABSTRACT Galaxies at high redshifts are a valuable tool for studying cosmic dawn, therefore it is crucial to reliably identify these galaxies. Here, we present an unambiguous and first simultaneous ...detection of both the Ly emission and the Lyman break from a z = 7.512 0.004 galaxy, observed in the Faint Infrared Grism Survey (FIGS). These spectra, taken with the G102 grism on the Hubble Space Telescope (HST), show a significant emission line detection ( 6 ) in two observational position angles (PAs), with Ly line flux of 1.06 0.19 × 10 − 17 erg s − 1 cm − 2 . The line flux is nearly a factor of four higher than that in the archival MOSFIRE spectroscopic observations. This is consistent with other recent observations, implying that ground-based near-infrared spectroscopy underestimates the total emission line fluxes, and if confirmed, can have strong implications for reionization studies that are based on ground-based Ly measurements. A 4 detection of the NV line in one PA also suggests a weak active galactic nucleus (AGN), and if confirmed, would make this source the highest-redshift AGN yet found. These observations from HST thus clearly demonstrate the sensitivity of the FIGS survey, and the capability of grism spectroscopy for studying the epoch of reionization.
Aims. The Ly luminosity function (LF) of high-redshift Ly emitters (LAEs) is one of the few observables of the re-ionization epoch accessible with 8-10 m class telescopes. The evolution of the LAE LF ...with redshift is dependent upon the physical evolution of LAEs and the ionisation state of the Universe towards the end of the Dark Ages. Methods. We performed a narrow-band imaging program at 1.06 m using CFHT/WIRCam. The observations target Ly emitters at redshift in the CFHT-LS D1 field. From these observations we derived a photometric sample of 7 LAE candidates at . Results. We derive luminosity functions for the full sample of seven objects and for subsamples of four objects. Assuming the brightest objects in our sample are real, we find that the resulting luminosity function is not consistent with previous work at lower redshifts. More definitive conclusions will require spectroscopic confirmation.
The authors observed three 7'.5 x 7'.5 fields with the HAWK-I instrument at the VLT with a narrow band filter centred at 1.06 mu m and targeting Ly alpha emitters at redshift z similar to 7.7. The ...fields were chosen for the availability of multiwavelength data. One field is a galaxy cluster, the Bullet Cluster, which allowed them to use gravitational amplification to probe luminosities that are fainter than in the field. The two other fields are subareas of the GOODS Chandra Deep Field South and CFHTLS-D4 deep field. They selected z = 7.7 LAE candidates from a variety of colour criteria, in particular from the absence of detection in the optical bands. They do not find any LAE candidates at z = 7.7 in ... down to a narrow band AB magnitude of similar to 26, which allows them to infer robust constraints on the Ly alpha LAE luminosity function at this redshift. (ProQuest: ... denotes formulae/symbols omitted.)
VANDELS is a deep spectroscopic survey, performed with the VIMOS instrument at VLT, aimed at studying in detail the physical properties of high-redshift galaxies. VANDELS targeted about 2100 sources ...at 1<z<6.5 in the CANDELS Chandra Deep-Field South (CDFS) and Ultra-Deep Survey (UDS) fields. In this paper we present the public release of the spectroscopic measurement catalogues from this survey, featuring emission and absorption line centroids, fluxes, and rest-frame equivalent widths obtained through a Gaussian fit, as well as a number of atomic and molecular indices (e.g. Lick) and continuum breaks (e.g. D4000), and including a correction to be applied to the error spectra. We describe the measurement methods and the validation of the codes that were used.
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