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de Bennassuti M.,University of Rome La Sapienza | de Bennassuti M.,National institute for astrophysics | Salvadori S.,Laboratoire dEtudes des Galaxies | Salvadori S.,University of Groningen | And 6 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2017

We study the impact of star-forming minihaloes, and the initial mass function (IMF) of Population III (Pop III) stars, on the Galactic halo metallicity distribution function (MDF) and on the properties of C-enhanced and C-normal stars at [Fe/H] < -3. For our investigation we use a data-constrained merger tree model for the MilkyWay formation, which has been improved to self-consistently describe the physical processes regulating star formation in minihaloes, including the poor sampling of the Pop III IMF.We find that only when star-forming minihaloes are included the low-Fe tail of the MDF is correctly reproduced, showing a plateau that is built up by C-enhanced metal-poor stars imprinted by primordial faint supernovae. The incomplete sampling of the Pop III IMF in inefficiently star-forming minihaloes (< 10-3M⊙ yr-1) strongly limits the formation of pair-instability supernovae (PISNe), with progenitor masses mPopIII = [140-260]M⊙, even when a flat Pop III IMF is assumed. Second-generation stars formed in environments polluted at > 50 per cent level by PISNe are thus extremely rare, corresponding to ≈0.25 per cent of the total stellar population at [Fe/H] < -2, which is consistent with recent observations. The low-Fe tail of the MDF strongly depends on the Pop III IMF shape and mass range. Given the current statistics, we find that a flat Pop III IMF model with mPopIII = [10-300]M⊙ is disfavoured by observations. We present testable predictions for Pop III stars extending down to lower masses, with mPopIII = [0.1-300]M⊙. © 2016 The Authors.

Mauduit J.-C.,California Institute of Technology | Lacy M.,U.S. National Radio Astronomy Observatory | Farrah D.,University of Sussex | Surace J.A.,California Institute of Technology | And 84 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2012

We present the Spitzer Extragalactic Representative Volume Survey (SERVS), an 18 deg2 mediumdeep survey at 3.6 and 4.5 μm with the postcryogenic Spitzer Space Telescope to ≈2 μJy (AB = 23:1) depth of five highly observed astronomical fields (ELAIS-N1, ELAIS-S1, Lockman Hole, Chandra Deep Field South, andXMMLSS). SERVSis designed to enable the study of galaxy evolution as a function of environment from z ~ 5 to the present day and is the first extragalactic survey that is both large enough and deep enough to put rare objects such as luminous quasars and galaxy clusters at z ≳ 1 into their cosmological context. SERVS is designed to overlap with several key surveys at optical, near- through far-infrared, submillimeter, and radio wavelengths to provide an unprecedented view of the formation and evolution of massive galaxies. In this article, we discuss the SERVS survey design, the data processing flow from image reduction and mosaicking to catalogs, and coverage of ancillary data from other surveys in the SERVS fields. We also highlight a variety of early science results from the survey. © 2012. The Astronomical Society of the Pacific. All rights reserved.

Bremer M.N.,Hh Wills Physics Laboratory | Silk J.,Denys Wilkinson Building | Davies L.J.M.,Hh Wills Physics Laboratory | Lehnert M.D.,Laboratoire dEtudes des Galaxies
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2010

We have carried out a redshift survey using the VIMOS spectrograph on the VLT towards the cosmic microwave background cold spot. A possible cause of the cold spot is the Integrated Sachs-Wolfe effect imprinted by an extremely large void (hundreds of Mpc in linear dimension) at intermediate or low redshifts. The redshift distribution of over seven hundred z < 1 emission-line galaxies drawn from an I-band flux limited sample of galaxies in the direction of the cold spot shows no evidence of a gap on scales of Δz ≳ 0.05 as would be expected if such a void existed at 0.35 < z < 1. There are troughs in the redshift distribution on smaller scales (Δz ≈ 0.01) indicating that smaller scale voids may connect regions separated by several degrees towards the cold spot. A comparison of this distribution with that generated from similarly sized subsamples drawn from widely spaced pointings of the VVDS survey does not indicate that the redshift distribution towards the cold spot is anomalous or that these small gaps can be uniquely attributed to real voids. © 2010 The Authors. Journal compilation © 2010 RAS.

Douglas L.S.,Laboratoire dEtudes des Galaxies | Douglas L.S.,H H Wills Physics Laboratory | Bremer M.N.,H H Wills Physics Laboratory | Lehnert M.D.,Laboratoire dEtudes des Galaxies | And 2 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2010

We present the global results of a large spectroscopic survey carried out in order to identify z~ 5 Lyman break galaxies (LBGs) across 10 widely separated ~45 arcmin2 fields to a depth of IAB= 26.3. The redshifts of seventy 4.6 < z < 5.6 LBGs were identified through their Lyα emission and/or a strong continuum break, with 38 sources showing detectable line emission of between 2.6 × 10-18 and 7 × 10-17 erg cm-2 s-1. Just over half of the spectroscopically confirmed z~ 5 galaxies have rest-frame Lyα equivalent widths above 20 Å, double the frequency of similarly strong line emitters in similar z~ 3 LBG samples. However, when reasonable corrections are made for the spectroscopically unconfirmed sources that are nevertheless at these redshifts in both samples, we find no significant difference in the frequency of high equivalent width line emitters between the samples. The rest-frame UV continuum slope of a typical z~ 5 line-emitting galaxy (as measured primarily from photometry, but also apparent in spectroscopy) is bluer than that of a typical break-only galaxy, a difference that is difficult to explain purely by differences in the ages of their stellar populations. Variation in metallicity and/or dust extinction can more straightforwardly account for this difference. If the correlation between metallicity and UV continuum slope identified at low redshift is applicable at z > 3, the typical z~ 5 LBGs have metallicities a factor of 3 lower than those of LBGs at z~ 3. Hubble Space Telescope imaging of a subset of the LBGs indicates that a large majority of the spectroscopically confirmed LBGs in our sample are members of multiple systems (on ~ arcsec scales) and/or show disturbed morphology. Using local LBG analogues as a model, this multiplicity could be explained either by super-starburst regions within a larger unseen structure or by a high incidence of merging events at this epoch. The current data cannot distinguish between these two possibilities. The surface density of z~ 5 LBGs in two of the 10 fields is considerably higher than in the rest. Both show clear spikes in their redshift distributions indicating strong three-dimensional clustering in these fields. Against an expectation of about one source per 0.1 in redshift between 4.8 < z < 5.6, one field has seven identified objects between 5.11 < z < 5.21 and the other has 17 between 4.95 < z < 5.15. Neither structure can be bound given their depth in redshift and probably extend beyond the observed fields. The three-dimensional distances between LBGs in the structures are too large for them to have triggered their starbursts through mutual gravitational interaction, and so it is likely that the short-lived LBGs represent only a small fraction of the baryons in the structures. © 2010 The Authors. Journal compilation © 2010 RAS.

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