arXiv subjects

F. Barrientos

Publications and source records attributed to F. Barrientos.

7 recordsLinked to original sources

arXiv2024

A lack of LAEs within 5Mpc of a luminous quasar in an overdensity at z=6.9: potential evidence of quasar negative feedback at protocluster scales

High-redshift quasars are thought to live in the densest regions of space which should be made evident by an overdensity of galaxies around them. However, campaigns to identify these overdensities through the search of Lyman Break Galaxies (LBGs) and Lyman $\alpha$ emitters (LAEs) have had mixed results. These may be explained by either the small field of view of some of the experiments, the broad redshift ranges targeted by LBG searches, and by the inherent large uncertainty of quasar redshifts estimated from UV emission lines, which makes it difficult to place the Ly-$\alpha$ emission line within a narrowband filter. Here we present a three square degree search ($\sim 1000$ pMpc) for LAEs around the $z=6.9$ quasar VIKJ2348-3054 using the Dark Energy CAMera (DECam), housed on the 4m Blanco telescope, finding 38 LAEs. The systemic redshift of VIK J2348--3054 is known from ALMA [CII] observations and place the Ly-$\alpha$ emission line of companions within the NB964 narrowband of DECam. This is the largest field of view LAE search around a $z>6$ quasar conducted to date. We find that this field is $\sim$ 10 times more overdense when compared to the Chandra Deep-Field South, observed previously with the same instrumental setup as well as several combined blank fields. This is strong evidence that VIKJ2348-3054 resides in an overdensity of LAEs over several Mpc. Surprisingly, we find a lack of LAEs within 5 physical Mpc of the quasar and take this to most likely be evidence of the quasar suppressing star formation in its immediate vicinity. This result highlights the importance of performing overdensity searches over large areas to properly assess the density of those regions of the Universe.

astro-ph.GA↗

arXiv2023

Directly constraining the spatial coherence of the $z\sim1$ circumgalactic medium

One of the biggest puzzles regarding the circumgalactic medium (CGM) is the structure of its cool ($T\sim10^4$ K) gas phase. While the kinematics of quasar absorption systems suggests the CGM is composed of a population of different clouds, constraining the clouds' extent and spatial distribution has proven challenging, both from the theoretical and observational points of view. In this work we study the spatial structure of the $z\sim 1$ CGM with unprecedented detail via resolved spectroscopy of giant gravitational arcs. We put together a sample of Mg II$\lambda\lambda 2796,2803$ detections obtained with VLT/MUSE in 91 spatially independent and contiguous sight-lines toward 3 arcs, each probing an isolated star-forming galaxy believed to be detected in absorption. We constrain the coherence scale of this gas ($C_{\rm{length}}$), which represents the spatial scale over which the Mg II equivalent width (EW) remains constant, by comparing EW variations measured across all sight-lines with empirical models. We find $1.4 <C_{\rm{length}}/\rm{kpc} <7.8$ (95% confidence). This measurement, of unprecedented accuracy, represents the scale over which the cool gas tends to cluster in separate structures. We argue that, if $C_{\rm{length}}$ is a universal property of the CGM, it needs to be reproduced by current and future theoretical models in order to understand the exact role of this medium in galaxy evolution.

astro-ph.GA↗

arXiv2021

Telltale signs of metal recycling in the circumgalactic medium of a $z \sim 0.77$ galaxy

We present gravitational-arc tomography of the cool-warm enriched circumgalactic medium (CGM) of an isolated galaxy (``G1'') at $z \approx 0.77$. Combining VLT/MUSE adaptive-optics and Magellan/MagE echelle spectroscopy we obtain partially-resolved kinematics of MgII in absorption and [OII] in emission. The unique arc configuration allows us to probe 42 spatially independent arc positions transverse to G1, plus 4 positions in front of it. The transverse positions cover G1's minor and major axes at impact parameters of $\approx 10-30$ kpc and $\approx 60$ kpc, respectively. We observe a direct kinematic connection between the cool-warm enriched CGM (traced by MgII) and the interstellar medium (traced by [OII]). This provides strong evidence for the existence of an extended disc that co-rotates with the galaxy out to tens of kiloparsecs. The MgII velocity dispersion ($\sigma \approx 30-100$ km s$^{-1}$, depending on position) is of the same order as the modeled galaxy rotational velocity ($v_{\rm rot} \approx 80$ km s$^{-1}$), providing evidence for the presence of a turbulent and pressure-supported CGM component. We regard the absorption to be modulated by a galactic-scale outflow, as it offers a natural scenario for the observed line-of-sight dispersion and asymmetric profiles observed against both the arcs and the galaxy. An extended enriched co-rotating disc together with the signatures of a galactic outflow, are telltale signs of metal recycling in the $z\sim 1$ CGM.

astro-ph.GA↗

arXiv2017

The ALMA Frontier Fields Survey - IV. Lensing-corrected 1.1 mm number counts in Abell 2744, MACSJ0416.1-2403 and MACSJ1149.5+2223

[abridged] Characterizing the number counts of faint, dusty star-forming galaxies is currently a challenge even for deep, high-resolution observations in the FIR-to-mm regime. They are predicted to account for approximately half of the total extragalactic background light at those wavelengths. Searching for dusty star-forming galaxies behind massive galaxy clusters benefits from strong lensing, enhancing their measured emission while increasing spatial resolution. Derived number counts depend, however, on mass reconstruction models that properly constrain these clusters. We estimate the 1.1 mm number counts along the line of sight of three galaxy clusters, i.e. Abell 2744, MACSJ0416.1-2403 and MACSJ1149.5+2223, which are part of the ALMA Frontier Fields Survey. We perform detailed simulations to correct these counts for lensing effects. We use several publicly available lensing models for the galaxy clusters to derive the intrinsic flux densities of our sources. We perform Monte Carlo simulations of the number counts for a detailed treatment of the uncertainties in the magnifications and adopted source redshifts. We find an overall agreement among the number counts derived for the different lens models, despite their systematic variations regarding source magnifications and effective areas. Our number counts span ~2.5 dex in demagnified flux density, from several mJy down to tens of uJy. Our number counts are consistent with recent estimates from deep ALMA observations at a 3$\sigma$ level. Below $\approx$ 0.1 mJy, however, our cumulative counts are lower by $\approx$ 1 dex, suggesting a flattening in the number counts. In our deepest ALMA mosaic, we estimate number counts for intrinsic flux densities $\approx$ 4 times fainter than the rms level. This highlights the potential of probing the sub-10 uJy population in larger samples of galaxy cluster fields with deeper ALMA observations.

astro-ph.GA↗

arXiv2013

Larger sizes of massive quiescent early-type galaxies in clusters than in the field at 0.8 < z < 1.5

[abridged] The mass-size relation of early-type galaxies (ETGs) has been largely studied in the last years to probe the mass assembly of the most massive objects in the Universe. In this paper, we focus on the mass-size relation of quiescent massive ETGs (Mstar/Msol > 3*10^10) living in massive clusters (M200 ~ 10^14 Mstar) at 0.8< z <1.5, as compared to those living in the field at the same epoch. Our sample contains ~ 400 ETGs in clusters and the same number in the field. Therefore, our sample is approximately an order of magnitude larger than previous studies in the same redshift range for galaxy clusters. We find that ETGs living in clusters are between ~30-50% larger than galaxies with the same stellar mass residing in the field. We parametrize the size using the mass-normalized size, gamma=Re/Mstar^0.57. The gamma distributions in both environments peak at the same position but the distributions in clusters are more skewed towards larger sizes. Since this size difference is not observed in the local Universe, the size evolution at fixed stellar mass from z~1.5 of cluster galaxies is less steep ((1+z)-0.53pm0.04) than the evolution of field galaxies ((1+z)-0.92pm0.04). The size difference seems to be essentially driven by the galaxies residing in the clusters cores (R<0.5*R200). If part of the size evolution is due to mergers, the difference we see between cluster and field galaxies could be due to higher merger rates in clusters at higher redshift, probably during the formation phase of the clusters when velocity dispersions are lower. We cannot exclude however that the difference is driven by newly quenched galaxies which are quenched more efficiently in clusters. The implications of these results for the hierarchical growth of ETGs will be discussed in a companion paper.

astro-ph.CO↗

arXiv2011

Scaling Relations and Overabundance of Massive Clusters at z>~1 from Weak-Lensing Studies with HST

We present weak gravitational lensing analysis of 22 high-redshift (z >~1) clusters based on Hubble Space Telescope images. Most clusters in our sample provide significant lensing signals and are well detected in their reconstructed two-dimensional mass maps. Combining the current results and our previous weak-lensing studies of five other high-z clusters, we compare gravitational lensing masses of these clusters with other observables. We revisit the question whether the presence of the most massive clusters in our sample is in tension with the current LambdaCDM structure formation paradigm. We find that the lensing masses are tightly correlated with the gas temperatures and establish, for the first time, the lensing mass-temperature relation at z >~ 1. For the power law slope of the M-TX relation (M propto T^{\alpha}), we obtain \alpha=1.54 +/- 0.23. This is consistent with the theoretical self-similar prediction \alpha=3/2 and with the results previously reported in the literature for much lower redshift samples. However, our normalization is lower than the previous results by 20-30%, indicating that the normalization in the M-TX relation might evolve. After correcting for Eddington bias and updating the discovery area with a more conservative choice, we find that the existence of the most massive clusters in our sample still provides a tension with the current Lambda CDM model. The combined probability of finding the four most massive clusters in this sample after marginalization over current cosmological parameters is less than 1%.

astro-ph.CO↗

arXiv2010

ACTPol: A polarization-sensitive receiver for the Atacama Cosmology Telescope

The six-meter Atacama Cosmology Telescope (ACT) in Chile was built to measure the cosmic microwave background (CMB) at arcminute angular scales. We are building a new polarization sensitive receiver for ACT (ACTPol). ACTPol will characterize the gravitational lensing of the CMB and aims to constrain the sum of the neutrino masses with ~0.05 eV precision, the running of the spectral index of inflation-induced fluctuations, and the primordial helium abundance to better than 1%. Our observing fields will overlap with the SDSS BOSS survey at optical wavelengths, enabling a variety of cross-correlation science, including studies of the growth of cosmic structure from Sunyaev-Zel'dovich observations of clusters of galaxies as well as independent constraints on the sum of the neutrino masses. We describe the science objectives and the initial receiver design.

astro-ph.IM↗