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<i>Spitzer Planck Herschel</i> Infrared Cluster (SPHerIC) survey: Candidate galaxy clusters at 1.3 < <i>z</i> < 3 selected by high star-formation rate
摘要： There is a lack of large samples of spectroscopically confirmed clusters and protoclusters at high redshifts, z > 1.5. Discovering and characterizing distant (proto-)clusters is important for yielding insights into the formation of large-scale structure and on the physical processes responsible for regulating star-formation in galaxies in dense environments. The Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey was initiated to identify these characteristically faint and dust-reddened sources during the epoch of their early assembly. We present Spitzer/IRAC observations of 82 galaxy (proto-)cluster candidates at 1.3 < zp < 3.0 that were vetted in a two step process: (1) using Planck to select by color those sources with the highest star-formation rates, and (2) using Herschel at higher resolution to separate out the individual red sources. The addition of the Spitzer data enables efficient detection of the central and massive brightest red cluster galaxies (BRCGs). We find that BRCGs are associated with highly significant, extended and crowded regions of IRAC sources which are more overdense than the field. This result corroborates our hypothesis that BRCGs within the Planck–Herschel sources trace some of the densest and actively star-forming proto-clusters in the early Universe. On the basis of a richness-mass proxy relation, we obtain an estimate of their mean masses which suggests our sample consists of some of the most massive clusters at z ≈ 2 and are the likely progenitors of the most massive clusters observed today.
关键词： galaxies: star formation,submillimeter: galaxies,infrared: galaxies,galaxies: evolution,galaxies: clusters: general,galaxies: high-redshift
更新于2025-09-23 15:23:52
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Photoionization models for extreme Ly <i>α λ</i> 1216 and Hell <i>λ</i> 1640 line ratios in quasar halos, and PopIII vs. AGN diagnostics
摘要： Aims. We explore potential mechanisms to produce extremely high Lyα/HeII ?ux ratios, or to enhance the observed number of Lyα photons per incident ionizing photon, in extended active galactic nucleus (AGN) photoionized nebulae at high-redshift. Methods. We computed models to simulate, in the low density regime, photoionization of interstellar gas by the radiation ?eld of a luminous AGN. We have explored the impact of ionization parameter, gas metallicity, ionizing spectrum, electron energy distribution, and cloud viewing angle on the relative ?uxes of Lyα, HeII and other lines, and on the observed number of Lyα photons per incident ionizing photon. We have compared our model results with recent observations of quasar Lyα halos at z ～ 3.5. Results. Low ionization parameter, a relatively soft or ?ltered ionizing spectrum, low gas metallicity, κ-distributed electron energies, or re?ection of Lyα photons by neutral hydrogen can all result in signi?cantly enhanced Lyα relative to other lines (≥10%), with log Lyα/HeII reaching values of up to 4.6. In the cases of low gas metallicity, re?ection by HI, or a hard or ?ltered ionizing spectrum, the observed number of Lyα photons per incident ionizing photon is itself signi?cantly enhanced above the nominal Case B value of 0.66 due to collisional excitation, reaching values as high as 5.3 in an “extreme case” model which combines several of these e?ects. We ?nd that at low gas metallicity (e.g. Z/Z(cid:12) = 0.1) the production of Lyα photons is predominantly via collisional excitation rather than by recombination. In addition, we ?nd that the collisional excitation of Lyα becomes much more e?cient if the ionizing continuum spectrum has been pre-?ltered through an optically thin screen of gas closer to the AGN (e.g. by a wide-angle, feedback-driven out?ow). We also show that the Lyα and HeII emission line ratios of a sample of previously studied quasars at z ～ 3.5 are consistent with AGN-photoionization of gas with moderate to low metallicity and/or low ionization parameter, without requiring exotic ionization or excitation mechanisms such as strong line-transfer e?ects. In addition, we present a set of UV-optical diagnostic diagrams to distinguish between photoionization by Pop III stars and photoionization by an AGN.
关键词： quasars: emission lines,galaxies: active,galaxies: ISM,galaxies: abundances,galaxies: high-redshift
更新于2025-09-23 15:23:52
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The VIMOS Ultra Deep Survey first data release: Spectra and spectroscopic redshifts of 698 objects up to <i>z</i> <sub/>spec</sub> ~ 6 in CANDELS
摘要： This paper describes the first data release (DR1) of the VIMOS Ultra Deep Survey (VUDS). The VUDS-DR1 is the release of all low-resolution spectroscopic data obtained in 276.9 arcmin2 of the CANDELS-COSMOS and CANDELS-ECDFS survey areas, including accurate spectroscopic redshifts zspec and individual spectra obtained with VIMOS on the ESO-VLT. A total of 698 objects have a measured redshift, with 677 galaxies, two type-I AGN, and a small number of 19 contaminating stars. The targets of the spectroscopic survey are selected primarily on the basis of their photometric redshifts to ensure a broad population coverage. About 500 galaxies have zspec > 2, 48 of which have zspec > 4; the highest reliable redshifts reach beyond zspec = 6. This data set approximately doubles the number of galaxies with spectroscopic redshifts at z > 3 in these fields. We discuss the general properties of the VUDS–DR1 sample in terms of the spectroscopic redshift distribution, the distribution of Lyman-α equivalent widths, and physical properties including stellar masses M* and star formation rates derived from spectral energy distribution fitting with the knowledge of zspec. We highlight the properties of the most massive star-forming galaxies, noting the wide range in spectral properties, with Lyman-α in emission or in absorption, and in imaging properties with compact, multi-component, or pair morphologies. We present the catalogue database and data products. All VUDS-DR1 data are publicly available and can be retrieved from a dedicated query-based database. Future VUDS data releases will follow this VUDS-DR1 to give access to the spectra and associated measurement of ～8000 objects in the full ～1 square degree of the VUDS survey.
关键词： surveys,cosmology: observations,galaxies: high-redshift,galaxies: distances and redshifts,catalogs
更新于2025-09-23 15:23:52
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Beamed Ly <i>α</i> emission through outflow-driven cavities
摘要： We investigate the radiative transfer of Lyα photons through simplified anisotropic gas distributions, which represent physically motivated extensions of the popular shell models. Our study is motivated by the notion that (i) shell models do not always reproduce observed Lyα spectral line profiles; (ii) (typical) shell models do not allow for the escape of ionizing photons; and (iii) the observation and expectation that winds are more complex, anisotropic phenomena. We examine the influence of inclination on the Lyα spectra, relative fluxes and escape fractions. We find the flux to be enhanced/suppressed by factors up to a few depending on the parameter range of the models, corresponding to a boost in equivalent width of the same amplitude if we neglect dust. In general, lower mean optical depths tend to reduce the impact of anisotropies as is expected. We find a correlation between an observed peak in the – occasionally triple-peaked – spectrum at the systemic velocity and the existence of a low optical depth cavity along the line of sight. This can be of importance in the search for ionizing photons leaking from high- redshift galaxies since these photons will also be able to escape through the cavity.
关键词： radiative transfer,galaxies: high-redshift
更新于2025-09-23 15:23:52
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Cosmic happenstance: 24-μm selected, multicomponent Herschel sources are line-of-sight projections
摘要： In this paper, we investigate the physical associations between blended far-infrared (FIR)-emitting galaxies, in order to identify the level of line-of-sight projection contamination in the single-dish Herschel data. Building on previous work, and as part of the Herschel Extragalactic Legacy Project, we identify a sample of galaxies in the COSMOS field, which are found to be both FIR-bright (typically ～15 mJy) and blended within the Herschel 250-μm beam. We identify a spectroscopic or photometric redshift for each FIR-bright source. We conduct a joint probability distribution analysis on the redshift probability density functions to determine the fraction of the FIR sources with multiple FIR-bright counterparts that are likely to be found at consistent (Δz < 0.01) redshifts. We find that only three (0.4 per cent) of the pair permutations between counterparts are >50 per cent likely to be at consistent redshifts. A majority of counterparts (72 per cent) have no overlap in their redshift probability distributions whatsoever. This is in good agreement with the results of recent simulations, which indicate that single-dish observations of the FIR sky should be strongly contaminated by line-of-sight projection effects. We conclude that for our sample of 3.6- and 24-μm selected, FIR-bright objects in the COSMOS field, the overwhelming majority of multicomponent FIR systems are line-of-sight projections within the 18.1-arcsec Herschel beam, rather than physical associations.
关键词： galaxies: statistics,galaxies: starburst,galaxies: star formation,galaxies: high redshift
更新于2025-09-23 15:22:29
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MASSIV: Mass Assembly Survey with SINFONI in VVDS
摘要： Aims. The MASSIV (Mass Assembly Survey with SINFONI in VVDS) project aims at finding constraints on the different processes involved in galaxy evolution. This study proposes to improve understanding of the galaxy mass assembly through chemical evolution using metallicity as a tracer of the star formation and interaction history. Methods. We analysed the full sample of MASSIV galaxies for which a metallicity estimate has been possible, the 48 star-forming galaxies at z ～ 0.9?1.8, and computed the integrated values of some of the fundamental parameters, such as stellar mass, metallicity, and star formation rate (SFR). The sample of star-forming galaxies at similar redshifts from zCOSMOS was also combined with the MASSIV sample. We studied the cosmic evolution of the mass-metallicty relation, together with the effect of close environment and galaxy kinematics on this relation. We then focussed on the so-called fundamental metallicity relation and other relations between stellar mass, SFR, and metallicity. We investigated whether these relations are really fundamental, i.e. if they do not evolve with redshift. Results. The MASSIV galaxies follow the expected mass-metallicity relation for their median redshift. We find, however, a significant difference between isolated and interacting galaxies as found for local galaxies: interacting galaxies tend to have a lower metallicity. The study of the relation between stellar mass, SFR, and metallicity gives such large scattering for our sample, even combined with zCOSMOS, that it is difficult to confirm any fundamental relation.
关键词： galaxies: abundances,galaxies: high-redshift,galaxies: fundamental parameters,galaxies: evolution
更新于2025-09-23 15:22:29
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Deep <i>R</i> -band counts of <i>z</i> ≈ 3 Lyman-break galaxy candidates with the LBT
摘要： Aims. We present a deep multiwavelength imaging survey (UGR) in 3 different fields, Q0933, Q1623, and COSMOS, for a total area of ～1500 arcmin2. The data were obtained with the Large Binocular Camera on the Large Binocular Telescope. Methods. To select our Lyman-break galaxy (LBG) candidates, we adopted the well established and widely used color-selection criterion (U ? G vs. G ? R). One of the main advantages of our survey is that it has a wider dynamic color range for U-dropout selection than in previous studies. This allows us to fully exploit the depth of our R-band images, obtaining a robust sample with few interlopers. In addition, for 2 of our fields we have spectroscopic redshift information that is needed to better estimate the completeness of our sample and interloper fraction. Results. Our limiting magnitudes reach 27.0(AB) in the R band (5σ) and 28.6(AB) in the U band (1σ). This dataset was used to derive LBG candidates at z ≈ 3. We obtained a catalog with a total of 12 264 sources down to the 50% completeness magnitude limit in the R band for each field. We find a surface density of ～3 LBG candidates arcmin?2 down to R = 25.5, where completeness is ≥95% for all 3 fields. This number is higher than the original studies, but consistent with more recent samples.
关键词： surveys,ultraviolet: galaxies,galaxies: high-redshift,galaxies: photometry,catalogs
更新于2025-09-23 15:22:29
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The WIRCam Ultra Deep Survey (WUDS)
摘要： The aim of this paper is to introduce the WIRCam Ultra Deep Survey (WUDS), a near-IR photometric survey carried out at the CFH Telescope in the field of the CFHTLS-D3 field (Groth Strip). WUDS includes four near-IR bands (Y, J, H and Ks) over a field of view of ～400 arcmin2. The typical depth of WUDS data reaches between ～26.8 in Y and J, and ～26 in H and Ks (AB, 3σ in 1.3'' aperture), whereas the corresponding depth of the CFHTLS-D3 images in this region ranges between 28.6 and 29 in ugr, 28.2 in i and 27.1 in z (same S/N and aperture). The area and depth of this survey were specifically tailored to set strong constraints on the cosmic star formation rate and the luminosity function brighter or around L* in the z ～ 6?10 redshift domain, although these data are also useful for a variety of extragalactic projects. This first paper is intended to present the properties of the public WUDS survey in details: catalog building, completeness and depth, number counts, photometric redshifts, and global properties of the galaxy population. We have also concentrated on the selection and characterization of galaxy samples at z ～ [4.5?7] in this field. For these purposes, we include an adjacent shallower area of ～1260 arcmin2 in this region, extracted from the WIRCam Deep Survey (WIRDS), and observed in J, H and Ks bands. UV luminosity functions were derived at z ～ 5 and z ～ 6 taking advantage from the fact that WUDS covers a particularly interesting regime at intermediate luminosities, which allows a combined determination of M* and Φ* with increased accuracy. Our results on the luminosity function are consistent with a small evolution of both M* and Φ* between z = 5 and z = 6, irrespective of the method used to derive them, either photometric redshifts applied to blindly-selected dropout samples or the classical Lyman Break Galaxy color-preselected samples. Our results lend support to higher Φ* determinations at z = 6 than usually reported. The selection and combined analysis of different galaxy samples at z ≥ 7 will be presented in a forthcoming paper, as well as the evolution of the UV luminosity function between z ～ 4.5 and 9. WUDS is intended to provide a robust database in the near-IR for the selection of targets for detailed spectroscopic studies, in particular for the EMIR/GTC GOYA Survey.
关键词： surveys,first stars,reionization,galaxies: high-redshift,dark ages
更新于2025-09-23 15:22:29
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The [CII] 158 <i>μ</i> m line emission in high-redshift galaxies
摘要： Gas is a crucial component of galaxies, providing the fuel to form stars, and it is impossible to understand the evolution of galaxies without knowing their gas properties. The [CII] fine structure transition at 158 μm is the dominant cooling line of cool interstellar gas, and is the brightest of emission lines from star forming galaxies from FIR through metre wavelengths, almost unaffected by attenuation. With the advent of ALMA and NOEMA, capable of detecting [CII]-line emission in high-redshift galaxies, there has been a growing interest in using the [CII] line as a probe of the physical conditions of the gas in galaxies, and as a star formation rate (SFR) indicator at z ≥ 4. In this paper, we have used a semi-analytical model of galaxy evolution (G.A.S.) combined with the photoionisation code CLOUDY to predict the [CII] luminosity of a large number of galaxies (25 000 at z (cid:39) 5) at 4 ≤ z ≤ 8. We assumed that the [CII]-line emission originates from photo-dominated regions. At such high redshift, the CMB represents a strong background and we discuss its effects on the luminosity of the [CII] line. We studied the L[CII]–SFR and L[CII]–Zg relations and show that they do not strongly evolve with redshift from z = 4 and to z = 8. Galaxies with higher [CII] luminosities tend to have higher metallicities and higher SFRs but the correlations are very broad, with a scatter of about 0.5 and 0.8 dex for L[CII]–SFR and L[CII]–Zg, respectively. Our model reproduces the L[CII]–SFR relations observed in high-redshift star-forming galaxies, with [CII] luminosities lower than expected from local L[CII]–SFR relations. Accordingly, the local observed L[CII]–SFR relation does not apply at high-z (z (cid:38) 5), even when CMB effects are ignored. Our model naturally produces the [CII] deficit (i.e. the decrease of L[CII]/LIR with LIR), which appears to be strongly correlated with the intensity of the radiation field in our simulated galaxies. We then predict the [CII] luminosity function, and show that it has a power law form in the range of L[CII] probed by the model (1 × 107–2 × 109 L(cid:12) at z = 6) with a slope α = ?1. The slope is not evolving from z = 4 to z = 8 but the number density of [CII]-emitters decreases by a factor of 20×. We discuss our predictions in the context of current observational estimates on both the differential and cumulative luminosity functions.
关键词： galaxies: high-redshift,galaxies: ISM,galaxies: evolution
更新于2025-09-23 15:21:21
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Recovering the systemic redshift of galaxies from their Lyman alpha line profile
摘要： The Lyman alpha (Ly α) line of Hydrogen is a prominent feature in the spectra of star-forming galaxies, usually redshifted by a few hundreds of km s?1 compared to the systemic redshift. This large offset hampers follow-up surveys, galaxy pair statistics, and correlations with quasar absorption lines when only Ly α is available. We propose diagnostics that can be used to recover the systemic redshift directly from the properties of the Ly α line pro?le. We use spectroscopic observations of Ly α emitters for which a precise measurement of the systemic redshift is available. Our sample contains 13 sources detected between z ≈ 3 and z ≈ 6 as part of various multi-unit spectroscopic explorer guaranteed time observations. We also include a compilation of spectroscopic Ly α data from the literature spanning a wide redshift range (z ≈ 0–8). First, restricting our analysis to double-peaked Ly α spectra, we ?nd a tight correlation between the velocity offset of the red peak with respect to the systemic redshift, V red peak, and the separation of the peaks. Secondly, we ?nd a correlation between V red peak and the full width at half-maximum of the Ly α line. Fitting formulas to estimate systemic redshifts of galaxies with an accuracy of ≤100 km s?1, when only the Ly α emission line is available, are given for the two methods.
关键词： ultraviolet: galaxies,galaxies: starburst,galaxies: statistics,galaxies: high-redshift
更新于2025-09-23 15:21:01