The VIMOS Ultra Deep Survey

Guaita, L.; Talia, M.; Pentericci, L.; Verhamme, Anne; Cassata, P.; Lemaux, B. C.; Orlitová, Ivana; Ribeiro, B.; Schaerer, D.; Zamorani, G.; Garilli, B.; Brun, V. Le; Fèvre, O. Le; Maccagni, D.; Tasca, L.; Thomas, Romain; Vanzella, E.; Zucca, E.; Amorín, R.; Bardelli, S.; Castellano, M.; Grazian, A.; Hathi, N. P.; Koekemoer, Anton M.; Marchi, F.

doi:10.1051/0004-6361/201730603

Cited by 27 publications

(41 citation statements)

References 94 publications

(116 reference statements)

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“…The three redshift samples span different dynamic ranges in EW Lyα , with the z ∼ 2 galaxies having on average the weakest Lyα and the z ∼ 4 showing the strongest. The z ∼ 2 and z ∼ 4 measurements show a clear trend of less redshifted Lyα centroid with stronger emission, similar to what has been found for LAEs in both individual and composite spectra at z ∼ 2 − 4 (Erb et al 2014;Guaita et al 2017), while for the z ∼ 3 sample there does not appear to be a dependence between these two parameters. Although the correlation between Lyα kinematics and strength is not conclusive at z ∼ 3 based only on our measurements, given previous kinematics studies of Lyα at this redshift (e.g., Shapley et al 2003), we believe that this relation holds at z ∼ 3 as well.…”

Section: Lyα Kinematicssupporting

confidence: 85%

The Redshift Evolution of Rest-UV Spectroscopic Properties in Lyman-break Galaxies at z ∼ 2–4

Shapley

Reddy

et al. 2018

ApJ

113

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We present the first comprehensive evolutionary analysis of the rest-frame UV spectroscopic properties of star-forming galaxies at z ∼ 2 − 4. We match samples at different redshifts in UV luminosity and stellar mass, and perform systematic measurements of spectral features and stellar population modeling. By creating composite spectra grouped according to Lyα equivalent width (EW), and various galaxy properties, we study the evolutionary trends among Lyα, low-and high-ionization interstellar (LIS and HIS) absorption features, and integrated galaxy properties. We also examine the redshift evolution of Lyα and LIS absorption kinematics, and fine-structure emission EWs. The connections among the strengths of Lyα, LIS lines, and dust extinction are redshift-independent, as is the decoupling of Lyα and HIS line strengths, and the bulk outflow kinematics as traced by LIS lines. Stronger Lyα emission is observed at higher redshift at fixed UV luminosity, stellar mass, SFR, and age. Much of this variation in average Lyα strength with redshift, and the variation in Lyα strength at fixed redshift, can be explained in terms of variations in neutral gas covering fraction and/or dust content in the ISM and CGM. However, based on the connection between Lyα and C iii] emission strengths, we additionally find evidence for variations in the intrinsic production rate of Lyα photons at the highest Lyα EWs. The challenge now is to understand the observed evolution in neutral gas covering fraction and dust extinction within a coherent model for galaxy formation, and make robust predictions for the escape of ionizing radiation at z > 6.We applied fixed redshift cuts to the LRIS, DEIMOS, and FORS2 datasets to define the z ∼ 2, 3, and 4 samples. We considered galaxies with z < 2.7 to be in the z ∼ 2 sample, galaxies with 2.7 z < 3.4 to be in the z ∼ 3 sample, and those with z 3.4 to be in the z ∼ 4 sample. The application of the redshift cuts results in 671, 352, and 80 objects (91 spectra) in the z ∼ 2, z ∼ 3, and z ∼ 4 samples, respectively. Figure 1 shows the redshift histograms of the z ∼ 2, 3 and 4 samples defined by fixed redshift cuts, with median redshifts of 2.25, 2.93, and 3.86, respectively. In practice, the z ∼ 2 and z ∼ 3 samples are all probed with LRIS data, while the z ∼ 4 sample is mainly covered by DEIMOS and FORS2 spectra, with a small addition of objects observed with LRIS. SED Fitting

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Section: Lyα Kinematicssupporting

confidence: 85%

The Redshift Evolution of Rest-UV Spectroscopic Properties in Lyman-break Galaxies at z ∼ 2–4

Shapley

Reddy

et al. 2018

ApJ

113

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“…The Spearman rank correlation coefficient for this relation is 0.44, with a significance that is > 2σ. This relation has been previously observed by Guaita et al (2017) using stacks of z ∼ 3 star forming galaxies. We discuss this trend and its interpretation in the next Section.…”

Section: Correlations With Is Shiftsupporting

confidence: 80%

“…The relation with Lyα ext has been previously observed by Guaita et al (2017), using stacks of VUDS galaxies at z ∼ 3, although their definition of Lyα extension was slightly different than ours since they subtracted in quadrature to the Lyα ext , the UV continuum to implicitly consider the deconvolution with the PSF of the observations. We now find a similar correlation also using individual objects.…”

Section: -Ew(lyα) Vs Ew(ciii])mentioning

confidence: 72%

The VANDELS survey: the role of ISM and galaxy physical properties in the escape of Lyα emission in z ∼ 3.5 star-forming galaxies

Marchi

Pentericci

Guaita

et al. 2019

A&A

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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.

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“…It also is a powerful tool to study conditions in the interstellar medium (ISM), both at low and high redshift (e.g. Hayes et al 2013Hayes et al , 2014Verhamme et al 2015;Guaita et al 2017). Lyα resonantly scatters off neutral hydrogen, which results in strong radiative transfer effects both in real and frequency space.…”

Section: Introductionmentioning

confidence: 99%

Puzzling Lyman-alpha line profiles in green pea galaxies

Orlitová

Verhamme

Henry

et al. 2018

A&A

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Context. The Lyman-alpha (Lyα) line of hydrogen is of prime importance for detecting galaxies at high redshift. For a correct data interpretation, numerical radiative transfer models are necessary due to Lyα resonant scattering off neutral hydrogen atoms. Aims. Recent observations have discovered an escape of ionizing Lyman-continuum radiation from a population of compact, actively star-forming galaxies at redshift z ∼ 0.2 − 0.3, also known as "green peas". For the potential similarities with high-redshift galaxies and impact on the reionization of the universe, we study the green pea Lyα spectra, which are mostly double-peaked, unlike in any other galaxy sample. If the double peaks are a result of radiative transfer, they can be a useful source of information on the green pea interstellar medium and ionizing radiation escape. Methods. We select a sample of twelve archival green peas and we apply numerical radiative transfer models to reproduce the observed Lyα spectral profiles, using the geometry of expanding, homogeneous spherical shells. We use ancillary optical and ultraviolet data to constrain the model parameters, and we evaluate the match between the models and the observed Lyα spectra. As a second step, we allow all the fitting parameters to be free, and examine the agreement between the interstellar medium parameters derived from the models and those from ancillary data. Results. The peculiar green pea double-peaked Lyα line profiles are not correctly reproduced by the constrained shell models. Conversely, unconstrained models fit the spectra, but parameters derived from the best-fitting models are not in agreement with the ancillary data. In particular: 1) the best-fit systemic redshifts are larger by 10 -250 km s −1 than those derived from optical emission lines; 2) the double-peaked Lyα profiles are best reproduced with low-velocity ( 150 km s −1 ) outflows that contradict the observed ultraviolet absorption lines of low-ionization-state elements with characteristic velocities as large as 300 km s −1 ; and 3) the models need to consider intrinsic Lyα profiles that are on average three times broader than the observed Balmer lines. Conclusions. Differences between the modelled and observed velocities are larger for targets with prominent Lyα blue peaks. The blue peak position and flux appear to be connected to low column densities of neutral hydrogen, leading to Lyα and Lyman-continuum escape. This is at odds with the kinematic origin of the blue peak in the homogeneous shell models. Additional modelling is needed to explore alternative geometries such as clumpy media and non-recombination Lyα sources to further constrain the role and significance of the Lyα double peaks.

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The VIMOS Ultra Deep Survey

Cited by 27 publications

References 94 publications

The Redshift Evolution of Rest-UV Spectroscopic Properties in Lyman-break Galaxies at z ∼ 2–4

The Redshift Evolution of Rest-UV Spectroscopic Properties in Lyman-break Galaxies at z ∼ 2–4

The VANDELS survey: the role of ISM and galaxy physical properties in the escape of Lyα emission in z ∼ 3.5 star-forming galaxies

Puzzling Lyman-alpha line profiles in green pea galaxies

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