Use of bending beam rheometer test for rheological analysis of asphalt emulsion-cement mastics in cold in-place recycling

This paper focused on exploiting the potential of the bending beam rheometer (BBR) test for analyzing asphalt emulsion-cement (AEC) mastics tailored for cold in-place recycling applications in the first weeks of curing, i.e. phase which implies the coexistence of viscoelastic and brittle materials. A consistent modified BBR testing protocol, which includes the experimental solutions devised for the practical execution of these unconventional rheometric measurements (sample preparation and test procedure), was proposed. The authors suggested to introduce glass microspheres, acting as "inert solid skeleton", in the production of AEC mastics for BBR prismatic beams, to study the interaction between asphalt emulsion and cement in thin film and to limit the specimens' shrinkage and warpage during the curing period. Finally, a feasibility study for validating the new modified experimental setup was presented, highlighting, with an explanatory overview of the types of results that can be expected, the macroscopic behaviors of some AEC mastics as a function of different parameters (asphalt binder to cement ratio, curing time and temperature). (C) 2019 Elsevier Ltd. All rights reserved

The VIMOS-VLT Deep Survey: Dependence of galaxy clustering on stellar mass

We have investigated the dependence of galaxy clustering on their stellar mass at z~1, using the data from the VIMOS-VLT Deep Survey (VVDS). We have measured the projected two-point correlation function of galaxies, wp(rp) for a set of stellar mass selected samples at an effective redshift =0.85. We have control and quantify all effects on galaxy clustering due to the incompleteness of our low mass samples. We find that more massive galaxies are more clustered. When compared to similar results at z~0.1 in the SDSS, we observed no evolution of the projected correlation function for massive galaxies. These objects present a stronger linear bias at z~1 with respect to low mass galaxies. As expected, massive objects at high redshift are found in the highest pics of the dark matter density field.Comment: 4 pages, 2 figures, 43rd Rencontres de Moriond - March 15-22, 2008 - La Thuile (Val d'Aosta, Italy

The contribution of faint AGNs to the ionizing background at z~4

Finding the sources responsible for the hydrogen reionization is one of the most pressing issues in cosmology. Bright QSOs are known to ionize their surrounding neighborhood, but they are too few to ensure the required HI ionizing background. A significant contribution by faint AGNs, however, could solve the problem, as recently advocated on the basis of a relatively large space density of faint active nuclei at z>4. We have carried out an exploratory spectroscopic program to measure the HI ionizing emission of 16 faint AGNs spanning a broad U-I color interval, with I~21-23 and 3.6<z<4.2. These AGNs are three magnitudes fainter than the typical SDSS QSOs (M1450<~-26) which are known to ionize their surrounding IGM at z>~4. The LyC escape fraction has been detected with S/N ratio of ~10-120 and is between 44 and 100% for all the observed faint AGNs, with a mean value of 74% at 3.6<z<4.2 and -25.1<M1450<-23.3, in agreement with the value found in the literature for much brighter QSOs (M1450<~-26) at the same redshifts. The LyC escape fraction of our faint AGNs does not show any dependence on the absolute luminosities or on the observed U-I colors. Assuming that the LyC escape fraction remains close to ~75% down to M1450~-18, we find that the AGN population can provide between 16 and 73% (depending on the adopted luminosity function) of the whole ionizing UV background at z~4, measured through the Lyman forest. This contribution increases to 25-100% if other determinations of the ionizing UV background are adopted. Extrapolating these results to z~5-7, there are possible indications that bright QSOs and faint AGNs can provide a significant contribution to the reionization of the Universe, if their space density is high at M1450~-23.Comment: Accepted for publication on A&A, 16 pages, 22 figure

The VANDELS survey: Dust attenuation in star-forming galaxies at z=3−4\mathbf{z=3-4}

We present the results of a new study of dust attenuation at redshifts $3 < z < 4$ based on a sample of $236$ star-forming galaxies from the VANDELS spectroscopic survey. Motivated by results from the First Billion Years (FiBY) simulation project, we argue that the intrinsic spectral energy distributions (SEDs) of star-forming galaxies at these redshifts have a self-similar shape across the mass range $8.2 \leq$ log$(M_{\star}/M_{\odot}) \leq 10.6$ probed by our sample. Using FiBY data, we construct a set of intrinsic SED templates which incorporate both detailed star formation and chemical abundance histories, and a variety of stellar population synthesis (SPS) model assumptions. With this set of intrinsic SEDs, we present a novel approach for directly recovering the shape and normalization of the dust attenuation curve. We find, across all of the intrinsic templates considered, that the average attenuation curve for star-forming galaxies at $z\simeq3.5$ is similar in shape to the commonly-adopted Calzetti starburst law, with an average total-to-selective attenuation ratio of $R_{V}=4.18\pm0.29$. We show that the optical attenuation ($A_V$) versus stellar mass ($M_{\star}$) relation predicted using our method is consistent with recent ALMA observations of galaxies at $2<z<3$ in the \emph{Hubble} \emph{Ultra} \emph{Deep} \emph{Field} (HUDF), as well as empirical $A_V - M_{\star}$ relations predicted by a Calzetti-like law. Our results, combined with other literature data, suggest that the $A_V - M_{\star}$ relation does not evolve over the redshift range $0<z<5$, at least for galaxies with log$(M_{\star}/M_{\odot}) \gtrsim 9.5$. Finally, we present tentative evidence which suggests that the attenuation curve may become steeper at log$(M_{\star}/M_{\odot}) \lesssim 9.0$.Comment: 16 pages, 12 figures, accepted for publication in MNRA

The VANDELS survey: Dust attenuation in star-forming galaxies at z=3−4\mathbf{z=3-4}

We present the results of a new study of dust attenuation at redshifts $3 < z < 4$ based on a sample of $236$ star-forming galaxies from the VANDELS spectroscopic survey. Motivated by results from the First Billion Years (FiBY) simulation project, we argue that the intrinsic spectral energy distributions (SEDs) of star-forming galaxies at these redshifts have a self-similar shape across the mass range $8.2 \leq$ log$(M_{\star}/M_{\odot}) \leq 10.6$ probed by our sample. Using FiBY data, we construct a set of intrinsic SED templates which incorporate both detailed star formation and chemical abundance histories, and a variety of stellar population synthesis (SPS) model assumptions. With this set of intrinsic SEDs, we present a novel approach for directly recovering the shape and normalization of the dust attenuation curve. We find, across all of the intrinsic templates considered, that the average attenuation curve for star-forming galaxies at $z\simeq3.5$ is similar in shape to the commonly-adopted Calzetti starburst law, with an average total-to-selective attenuation ratio of $R_{V}=4.18\pm0.29$. We show that the optical attenuation ($A_V$) versus stellar mass ($M_{\star}$) relation predicted using our method is consistent with recent ALMA observations of galaxies at $2<z<3$ in the \emph{Hubble} \emph{Ultra} \emph{Deep} \emph{Field} (HUDF), as well as empirical $A_V - M_{\star}$ relations predicted by a Calzetti-like law. Our results, combined with other literature data, suggest that the $A_V - M_{\star}$ relation does not evolve over the redshift range $0<z<5$, at least for galaxies with log$(M_{\star}/M_{\odot}) \gtrsim 9.5$. Finally, we present tentative evidence which suggests that the attenuation curve may become steeper at log$(M_{\star}/M_{\odot}) \lesssim 9.0$.Comment: 16 pages, 12 figures, accepted for publication in MNRA

K-band Properties of Well-Sampled Groups of Galaxies

We use a sample of 55 groups and 6 clusters of galaxies ranging in mass from 7 x 10^11 Msun to 1.5 x 10^15 Msun to examine the correlation of the Ks-band luminosity with mass discovered by Lin et al. (2003). We use the 2MASS catalog and published redshifts to construct complete magnitude limited redshift surveys of the groups. From these surveys we explore the IR photometric properties of groups members including their IR color distribution and luminosity function. Although we find no significant difference between the group Ks luminosity function and the general field, there is a difference between the color distribution of luminous group members and their counterparts (generally background) in the field. There is a significant population of luminous galaxies with H-Ks > 0.35 which are rarely, if ever, members of the groups in our sample. The most luminous galaxies which populate the groups have a very narrow range of IR color. Over the entire mass range covered by our sample, the Ks luminosity increases with mass as L ~ M^(0.64 +/- 0.06) implying that the mass-to-light ratio in the Ks-band increases with mass. The agreement between this result and earlier investigations of essentially non-overlapping sets of systems shows that this window in galaxy formation and evolution is insensitive to the selection of the systems and to the details of the mass and luminosity computations.Comment: 38 pages, 9 figures, 2 tables. Accepted for publication on Astronomical Journa

Optical (VRI) Photometry in the Field of the Galaxy Cluster AC 118 at z=0.31

We present new photometric V-, R- and I-band data for the rich galaxy cluster AC 118 at z=0.31. The new photometry covers an area of 8.6x8.6 arcmin$^2$, corresponding to 2.9$\times$2.9 Mpc$^2$ (H$_0=50$ km s$^{-1}$ Mpc$^{-1}$, q$_0=0.5$ and $\Lambda = 0$). The data have been collected for a project aimed at studying galaxy evolution through the color-magnitude relation and the fundamental plane. We provide a catalogue including all the sources (N = 1206) detected in the cluster field. The galaxy sample is complete to V=22.8 mag (N_gal=574), R=22.3 mag (N_gal=649) and I=20.8 mag (N_gal=419). We give aperture magnitudes within a fixed aperture of 4.4 arcsec and Kron magnitudes. We also give photometric redshifts for 459 sources for which additional U- and K-band photometry is available. We derive and discuss the V- and R-band luminosity functions. The catalogue, which is distributed in electronic form, is intended as a tool for studies in galaxy evolution.Comment: 15 pages, 6 figures, A&A in pres

The VANDELS survey: A strong correlation between Lyα\alpha equivalent width and stellar metallicity at 3≤z≤5\mathbf{3\leq z \leq 5}

We present the results of a new study investigating the relationship between observed Ly$\alpha$ equivalent width ($W_{\lambda}$(Ly$\alpha$)) and the metallicity of the ionizing stellar population ($Z_{\star}$) for a sample of $768$ star-forming galaxies at $3 \leq z \leq 5$ drawn from the VANDELS survey. Dividing our sample into quartiles of rest-frame $W_{\lambda}$(Ly$\alpha$) across the range -58 \unicode{xC5} \lesssim $W_{\lambda}$(Ly$\alpha$) \lesssim 110 \unicode{xC5} we determine $Z_{\star}$ from full spectral fitting of composite far-ultraviolet (FUV) spectra and find a clear anti-correlation between $W_{\lambda}$(Ly$\alpha$) and $Z_{\star}$. Our results indicate that $Z_{\star}$ decreases by a factor $\gtrsim 3$ between the lowest $W_{\lambda}$(Ly$\alpha$) quartile ($\langle$$W_{\lambda}$(Ly$\alpha$)\rangle=-18\unicode{xC5}) and the highest $W_{\lambda}$(Ly$\alpha$) quartile ($\langle$$W_{\lambda}$(Ly$\alpha$)\rangle=24\unicode{xC5}). Similarly, galaxies typically defined as Lyman Alpha Emitters (LAEs; $W_{\lambda}$(Ly$\alpha$) >20\unicode{xC5}) are, on average, metal poor with respect to the non-LAE galaxy population ($W_{\lambda}$(Ly$\alpha$) \leq20\unicode{xC5}) with $Z_{\star}$$_{\rm{non-LAE}}\gtrsim 2 \times$ $Z_{\star}$$_{\rm{LAE}}$. Finally, based on the best-fitting stellar models, we estimate that the increasing strength of the stellar ionizing spectrum towards lower $Z_{\star}$ is responsible for $\simeq 15-25\%$ of the observed variation in $W_{\lambda}$(Ly$\alpha$) across our sample, with the remaining contribution ($\simeq 75-85\%$) being due to a decrease in the HI/dust covering fractions in low $Z_{\star}$ galaxies.Comment: 10 pages, 6 figures, MNRAS accepte