arXiv subjects

C. Hoyos

Publications and source records attributed to C. Hoyos.

At least 19 recordsLinked to original sources

arXiv2025

Pseudo-gauge invariant non-equilibrium density operator

We obtain a form of the local thermodynamic equilibrium density operator which is invariant under pseudo-gauge transformations of the stress-energy and the spin tensors. This operator is an excellent candidate to describe the dynamics of a system which is assumed to achieve local equilibrium from a pseudo-gauge invariant quantum state, a situation which is believed to occur, for instance, in nuclear collisions at very high energy. As a consequence of pseudo-gauge invariance, the ambiguity affecting the predictions of mean values of observables from a local equilibrium state can be removed.

nucl-th↗

arXiv2020

The evolution of galaxy scaling relations in clusters at 0.5<z<1.5

We present new gas kinematic observations with the OSIRIS instrument at the GTC for galaxies in the Cl1604 cluster system at z=0.9. These observations together with a collection of other cluster samples at different epochs analyzed by our group are used to study the evolution of the Tully-Fisher, velocity-size and stellar mass-angular momentum relations in dense environments over cosmic time. We use 2D and 3D spectroscopy to analyze the kinematics of our cluster galaxies and extract their maximum rotation velocities (Vmax). Our methods are consistently applied to all our cluster samples which make them ideal for an evolutionary comparison. Up to redshift one, our cluster samples show evolutionary trends compatible with previous observational results in the field and in accordance with semianalytical models and hydrodynamical simulations concerning the Tully-Fisher and velocity-size relations. However, we find a factor 3 drop in disk sizes and an average B-band luminosity enhancement of 2 mag by z=1.5. We discuss the role that different cluster-specific interactions may play in producing this observational result. In addition, we find that our intermediate-to-high redshift cluster galaxies follow parallel sequences with respect to the local specific angular momentum-stellar mass relation, although displaying lower angular momentum values in comparison with field samples at similar redshifts. This can be understood by the stronger interacting nature of dense environments with respect to the field.

astro-ph.GA↗

arXiv2016

The Herschel-ATLAS Data Release 1 Paper II: Multi-wavelength counterparts to submillimetre sources

This paper is the second in a pair of articles presenting data release 1 (DR1) of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), the largest single open-time key project carried out with the Herschel Space Observatory. The H-ATLAS is a wide-area imaging survey carried out in five photometric bands at 100, 160, 250, 350 and 500$μ$m covering a total area of 600deg$^2$. In this paper we describe the identification of optical counterparts to submillimetre sources in DR1, comprising an area of 161 deg$^2$ over three equatorial fields of roughly 12$^\circ$x4.5$^\circ$ centred at 9$^h$, 12$^h$ and 14.5$^h$ respectively. Of all the H-ATLAS fields, the equatorial regions benefit from the greatest overlap with current multi-wavelength surveys spanning ultraviolet (UV) to mid-infrared regimes, as well as extensive spectroscopic coverage. We use a likelihood-ratio technique to identify SDSS counterparts at r<22.4 for 250-$μ$m-selected sources detected at $\geq$ 4$σ$ ($\approx$28mJy). We find `reliable' counterparts (reliability R$\geq$0.8) for 44,835 sources (39 per cent), with an estimated completeness of 73.0 per cent and contamination rate of 4.7 per cent. Using redshifts and multi-wavelength photometry from GAMA and other public catalogues, we show that H-ATLAS-selected galaxies at $z<0.5$ span a wide range of optical colours, total infrared (IR) luminosities, and IR/UV ratios, with no strong disposition towards mid-IR-classified AGN in comparison with optical selection. The data described herein, together with all maps and catalogues described in the companion paper (Valiante et al. 2016), are available from the H-ATLAS website at www.h-atlas.org.

astro-ph.GA↗

arXiv2015

Holographic impurities and Kondo effect

Magnetic impurities are responsible for many interesting phenomena in condensed matter systems, notably the Kondo effect and quantum phase transitions. Here we present a holographic model of a magnetic impurity that captures the main physical properties of the large-spin Kondo effect. We estimate the screening length of the Kondo cloud that forms around the impurity from a calculation of entanglement entropy and show that our results are consistent with the g-theorem.

hep-th↗

arXiv2014

Colour matters: the effects of lensing on the positional offsets between optical and submillimetre galaxies in Herschel-ATLAS

We report an unexpected variation in the positional offset distributions between Herschel-ATLAS sub-millimetre (submm) sources and their optical associations, depending on both 250-μm signal-to-noise ratio and 250/350-μm colour. We show that redder and brighter submm sources have optical associations with a broader distribution of positional offsets than would be expected if these offsets were due to random positional errors in the source extraction. The observation can be explained by two possible effects: either red submm sources trace a more clustered population than blue ones, and their positional errors are increased by confusion; or red submm sources are generally at high redshifts and are frequently associated with low-redshift lensing structures which are identified as false counterparts. We perform various analyses of the data, including the multiplicity of optical associations, the redshift and magnitude distributions in H-ATLAS in comparison to HerMES, and simulations of weak lensing, and we conclude that the effects are most likely to be explained by widespread weak lensing of Herschel-SPIRE sources by foreground structures. This has important consequences for counterpart identification and derived redshift distributions and luminosity functions of submm surveys.

astro-ph.GA↗

arXiv2014

J-PAS: The Javalambre-Physics of the Accelerated Universe Astrophysical Survey

The Javalambre-Physics of the Accelerated Universe Astrophysical Survey (J-PAS) is a narrow band, very wide field Cosmological Survey to be carried out from the Javalambre Observatory in Spain with a purpose-built, dedicated 2.5m telescope and a 4.7 sq.deg. camera with 1.2Gpix. Starting in late 2015, J-PAS will observe 8500sq.deg. of Northern Sky and measure $0.003(1+z)$ photo-z for $9\times10^7$ LRG and ELG galaxies plus several million QSOs, sampling an effective volume of $\sim 14$ Gpc$^3$ up to $z=1.3$ and becoming the first radial BAO experiment to reach Stage IV. J-PAS will detect $7\times 10^5$ galaxy clusters and groups, setting constrains on Dark Energy which rival those obtained from its BAO measurements. Thanks to the superb characteristics of the site (seeing ~0.7 arcsec), J-PAS is expected to obtain a deep, sub-arcsec image of the Northern sky, which combined with its unique photo-z precision will produce one of the most powerful cosmological lensing surveys before the arrival of Euclid. J-PAS unprecedented spectral time domain information will enable a self-contained SN survey that, without the need for external spectroscopic follow-up, will detect, classify and measure $σ_z\sim 0.5\%$ redshifts for $\sim 4000$ SNeIa and $\sim 900$ core-collapse SNe. The key to the J-PAS potential is its innovative approach: a contiguous system of 54 filters with $145Å$ width, placed $100Å$ apart over a multi-degree FoV is a powerful "redshift machine", with the survey speed of a 4000 multiplexing low resolution spectrograph, but many times cheaper and much faster to build. The J-PAS camera is equivalent to a 4.7 sq.deg. "IFU" and it will produce a time-resolved, 3D image of the Northern Sky with a very wide range of Astrophysical applications in Galaxy Evolution, the nearby Universe and the study of resolved stellar populations.

astro-ph.CO↗

arXiv2013

H2O emission in high-z ultra-luminous infrared galaxies

Using IRAM PdBI we report the detection of H2O in six new lensed ultra-luminous starburst galaxies at high redshift, discovered in the Herschel H-ATLAS survey. The sources are detected either in the 2_{02}-1_{11} or 2_{11}-2_{02} H_2O emission lines with integrated line fluxes ranging from 1.8 to 14 Jy.km/s. The corresponding apparent luminosities are mu x L_H2O ~ 3-12 x 10^8 Lo, where mu is the lensing magnification factor (3 < mu < 12). These results confirm that H2O lines are among the strongest molecular lines in such galaxies, with intensities almost comparable to those of the high-J CO lines, and same profiles and line widths (200-900 km/s) as the latter. With the current sensitivity of PdBI, H2O can therefore easily be detected in high-z lensed galaxies (with F(500um) > 100 mJy) discovered in the Herschel surveys. Correcting the luminosities for lensing amplification, L_H2O is found to have a strong dependence on the IR luminosity, varying as ~L_IR^{1.2}. This relation which needs to be confirmed with better statistics, may indicate a role of radiative (IR) excitation of the H2O lines, and implies that high-z galaxies with L_IR >~ 10^13 Lo tend to be very strong emitters in H2O, that have no equivalent in the local universe.

astro-ph.CO↗

arXiv2012

H-ATLAS: The cosmic abundance of dust from the far-infrared background power spectrum

We present a measurement of the angular power spectrum of the cosmic far-infrared background (CFIRB) anisotropies in one of the extragalactic fields of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) at 250, 350 and 500 μm bands. Consistent with recent measurements of the CFIRB power spectrum in Herschel-SPIRE maps, we confirm the existence of a clear one-halo term of galaxy clustering on arcminute angular scales with large-scale two-halo term of clustering at 30 arcminutes to angular scales of a few degrees. The power spectrum at the largest angular scales, especially at 250 μm, is contaminated by the Galactic cirrus. The angular power spectrum is modeled using a conditional luminosity function approach to describe the spatial distribution of unresolved galaxies that make up the bulk of the CFIRB. Integrating over the dusty galaxy population responsible for the background anisotropies, we find that the cosmic abundance of dust, relative to the critical density, to be between Ω_dust=10^{-6} and 8 x 10^{-6} in the redshift range z ~ 0-3. This dust abundance is consistent with estimates of the dust content in the Universe using quasar reddening and magnification measurements in the SDSS.

astro-ph.CO↗

arXiv2012

Herschel-ATLAS: the far-infrared properties and star-formation rates of broad absorption line quasi-stellar objects

We have used data from the Herschel-ATLAS at 250, 350 and 500 μm to determine the far-infrared (FIR) properties of 50 Broad Absorption Line Quasars (BAL QSOs). Our sample contains 49 high-ionization BAL QSOs (HiBALs) and 1 low-ionization BAL QSO (LoBAL) which are compared against a sample of 329 non-BAL QSOs. These samples are matched over the redshift range 1.5 \leq z < 2.3 and in absolute i-band magnitude over the range -28 \leq M_{i} \leq -24. Of these, 3 BAL QSOs (HiBALs) and 27 non-BAL QSOs are detected at the > 5 sigma level. We calculate star-formation rates (SFR) for our individually detected HiBAL QSOs and the non-detected LoBAL QSO as well as average SFRs for the BAL and non-BAL QSO samples based on stacking the Herschel data. We find no difference between the HiBAL and non-BAL QSO samples in the FIR, even when separated based on differing BAL QSO classifications. Using Mrk 231 as a template, the weighted mean SFR is estimated to be \approx240\pm21 M_{\odot} yr^{-1} for the full sample, although this figure should be treated as an upper limit if AGN-heated dust makes a contribution to the FIR emission. Despite tentative claims in the literature, we do not find a dependence of {\sc C\,iv} equivalent width on FIR emission, suggesting that the strength of any outflow in these objects is not linked to their FIR output. These results strongly suggest that BAL QSOs (more specifically HiBALs) can be accommodated within a simple AGN unified scheme in which our line-of-sight to the nucleus intersects outflowing material. Models in which HiBALs are caught towards the end of a period of enhanced spheroid and black-hole growth, during which a wind terminates the star-formation activity, are not supported by the observed FIR properties.

astro-ph.CO↗

arXiv2012

The evolutionary connection between QSOs and SMGs: molecular gas in far-infrared luminous QSOs at z ~ 2.5

We present IRAM Plateau de Bure Interferometer observations of the 12CO(3-2) emission from two far-infrared luminous QSOs at z ~ 2.5 selected from the Herschel-ATLAS survey. These far-infrared bright QSOs were selected to have supermassive black holes (SMBHs) with masses similar to those thought to reside in sub-millimetre galaxies (SMGs) at z ~ 2.5; making them ideal candidates as systems in transition from an ultraluminous infrared galaxy phase to a sub-mm faint, unobscured, QSO. We detect 12CO(3-2) emission from both QSOs and we compare their baryonic, dynamical and SMBH masses to those of SMGs at the same epoch. We find that these far-infrared bright QSOs have similar dynamical but lower gas masses than SMGs. In particular we find that far-infrared bright QSOs have ~50+-23% less warm/dense gas than SMGs, which combined with previous results showing the QSOs lack the extended, cool reservoir of gas seen in SMGs, suggests that they are at a different evolutionary stage. This is consistent with the hypothesis that far-infrared bright QSOs represent a short (~1Myr) but ubiquitous phase in the transformation of dust obscured, gas-rich, starburst-dominated SMGs into unobscured, gas-poor, QSOs.

astro-ph.CO↗

arXiv2012

Mining the Herschel-ATLAS: submillimeter-selected blazars in equatorial fields

The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) provides an unprecedented opportunity to search for blazars at sub-mm wavelengths. We cross-matched the FIRST radio source catalogue with the 11655 sources brighter than 35 mJy at 500μm in the \sim 135 square degrees of the sky covered by the H-ATLAS equatorial fields at 9 h and 15 h, plus half of the field at 12 h. We found that 379 of the H-ATLAS sources have a FIRST counterpart within 10 arcsec, including 8 catalogued blazars (plus one known blazar that was found at the edge of one the H-ATLAS maps). To search for additional blazar candidates we have devised new diagnostic diagrams and found that known blazars occupy a region of the log(S500μm/S350μm) vs. log(S500μm/S1.4GHz) plane separated from that of the other sub-mm sources with radio counterparts. Using this diagnostic we have selected 12 further candidates that turn out to be scattered in the (r-z) vs. (u-r) plane or in the WISE colour-colour diagram proposed by Massaro et al. (2012), where known blazars are concentrated in well defined strips. This suggests that the majority of them either are not blazars or have spectral energy distributions contaminated by their host galaxies. A significant fraction of true blazars are found to be hosted by star-forming galaxies. This finding, supported by an analysis of blazars detected in Planck 545 and 857 GHz bands, is at odds with the notion that blazar hosts are passive ellipticals and indicates that the sub-mm selection is providing a novel prospect on blazar properties. Based on an inspection of the available photometric data, including the WISE all-sky survey, the unpublished VIKING survey and new radio observations, we tentatively estimate that there are 11 blazars with synchrotron flux density S500μm > 35mJy over the considered area. This result already allows us to constrain blazar evolution models.

astro-ph.CO↗

arXiv2012

A Comprehensive View of a Strongly Lensed Planck-Associated Submillimeter Galaxy

We present high-resolution maps of stars, dust, and molecular gas in a strongly lensed submillimeter galaxy (SMG) at z = 3.259. HATLAS12--00 is selected from the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) as a strong lens candidate mainly based on its unusually high 500um flux density (~300 mJy). It is the only high-redshift Planck detection in the 130 deg^2 H-ATLAS Phase 1 area. Keck Adaptive Optics images reveal a quadruply imaged galaxy in the K-band while the Submillimeter Array and the Extended Very Large Array show doubly imaged 880um and CO(1-0) sources, indicating differentiated distributions of the various components in the galaxy. In the source plane, the stars reside in three major kpc-scale clumps extended over ~1.6 kpc, the dust in a compact (~1 kpc) region ~3 kpc north of the stars, and the cold molecular gas in an extended (~7 kpc) disk ~5 kpc northeast of the stars. The emission from the stars, dust, and gas are magnified by ~17, 8, and 7 times, respectively, by four lensing galaxies at z ~ 1. Intrinsically, the lensed galaxy is a warm (T_dust ~ 40-65 K), hyper-luminous (L_IR ~ 1.7e13 Lsun; SFR ~ 2000 Msun/yr), gas-rich (M_gas/M_baryon ~ 70%), young (M_stellar/SFR ~ 20 Myr), and short-lived (M_gas/SFR ~ 40 Myr) starburst, without a significant active galactic nucleus. With physical properties similar to unlensed z > 2 SMGs, HATLAS12--00 offers a detailed view of a typical SMG through a powerful cosmic microscope.

astro-ph.CO↗

arXiv2012

Herschel-ATLAS: Planck sources in the Phase 1 fields

We present the results of a cross-correlation of the Planck Early Release Compact Source Catalog (ERCSC) with the catalog of Herschel-ATLAS sources detected in the Phase 1 fields, covering 134.55 deg2. There are 28 ERCSC sources detected by Planck at 857 GHz in this area. As many as 16 of them are probably high Galactic latitude cirrus; 10 additional sources can be clearly identified as bright, low-z galaxies; one further source is resolved by Herschel as two relatively bright sources; and the last is resolved into an unusual condensation of low-flux, probably high-redshift point sources, around a strongly lensed Herschel-ATLAS source at z = 3.26. Our results demonstrate that the higher sensitivity and higher angular resolution H-ATLAS maps provide essential information for the interpretation of candidate sources extracted from Planck sub-mm maps.

astro-ph.CO↗

arXiv2011

The HST/ACS Coma Cluster Survey: VII - Colour Gradients in Giant and Dwarf Early-Type Galaxies

Using deep, high-spatial resolution imaging from the HST ACS Coma Cluster Treasury Survey, we determine colour profiles of early-type galaxies in the Coma cluster. From 176 galaxies brighter than $M_\mathrm{F814W(AB)} = -15$ mag that are either spectroscopically confirmed members of Coma or identified by eye as likely members from their low surface brightness, data are provided for 142 early-type galaxies. Typically, colour profiles are linear against $\log(R)$, sometimes with a nuclear region of distinct, often bluer colour associated with nuclear clusters. Colour gradients are determined for the regions outside the nuclear components. We find that almost all colour gradients are negative, both for elliptical and lenticular galaxies. Most likely, earlier studies that report positive colour gradients in dwarf galaxies are affected by the bluer colours of the nuclear clusters, underlining that high resolution data are essential to disentangle the colour properties of the different morphological components in galaxies. Colour gradients of dwarf galaxies form a continuous sequence with those of elliptical galaxies, becoming shallower toward fainter magnitudes. Interpreting the colours as metallicity tracers, our data suggest that dwarfs as well as giant early-type galaxies in the Coma cluster are less metal rich in their outer parts. We do not find evidence for environmental influence on the gradients, although we note that most of our galaxies are found in the central regions of the cluster. For a subset of galaxies with known morphological types, S0 galaxies have less steep gradients than elliptical galaxies.

astro-ph.GA↗

arXiv2007

Stellar Populations Found in the Central kpc of Four Luminous Compact Blue Galaxies at Intermediate Redshift

We investigate the star formation history of the central regions of four Luminous Compact Blue Galaxies (LCBGs). LCBGs are blue (B-V<0.6), compact (MU_B<21.5 mag arcsec^-2) galaxies with absolute magnitudes M_B brighter than -17.5. The LCBGs analyzed here are located at 0.436<z<0.525. They are among the most luminous (M_B < -20.5), blue (B-V < 0.4) and high surface brightness (MU_B < 19.0 mag arcsec^-2) of this population. The observational data used were obtained with the HST/STIS spectrograph, the HST/WF/PC-2 camera and the HST/NICMOS first camera. We find evidence for multiple stellar populations. One of them is identified as the ionizing population, and the other one corresponds to the underlying stellar generation. The estimated masses of the inferred populations are compatible with the dynamical masses, which are typically 2--10x 10^9 M_sun. Our models also indicate that the first episodes of star formation the presented LCBGs underwent happened between 5 and 7 Gyr ago. We compare the stellar populations found in LCBGs with the stellar populations present in bright, local HII galaxies, nearby spheroidal systems and Blue Compact Dwarf Galaxies. It turns out that the underlying stellar populations of LCBGs are similar yet bluer to those of local HII galaxies. It is also the case that the passive color evolution of the LCBGs could convert them into local Spheroidal galaxies if no further episode of star formation takes place. Our results help to impose constraints on evolutionary scenarios for the population of LCBGs found commonly at intermediate redshifts.

astro-ph↗

arXiv2006

Dynamical Higgs potentials with a landscape

We consider one-loop effective potentials for adjoint Higgs fields that originate from flat holonomies in toroidal compactification of gauge theories. We show that such potentials are "landscape-like" for large gauge groups and generic non-supersymmetric matter representations. In particular, there is a large number of vacua with similar local properties, scanning a broad band of vacuum energies.

hep-th↗

arXiv2006

Large N orbifold field theories on the twisted torus

We study the planar equivalence of orbifold field theories on a small three-torus with twisted boundary conditions, generalizing the analysis of hep-th/0507267. The nonsupersymmetric orbifold models exhibit different large N dynamics from their supersymmetric "parent" counterparts. In particular, a moduli space of Abelian zero modes is lifted by an $O(N^2)$ potential in the "daughter" theories. We also find disagreement between the number of discrete vacua of both theories, due to fermionic zero modes in the parent theory, as well as the values of semiclassical tunneling contributions to fermionic correlation functions, induced by fractional instantons.

hep-th↗

arXiv2005

Small volume expansion of almost supersymmetric large N theories

We consider the small-volume dynamics of nonsupersymmetric orbifold and orientifold field theories defined on a three-torus, in a test of the claimed planar equivalence between these models and appropriate supersymmetric ``parent models". We study one-loop effective potentials over the moduli space of flat connections and find that planar equivalence is preserved for suitable averages over the moduli space. On the other hand, strong nonlinear effects produce local violations of planar equivalence at special points of moduli space. In the case of orbifold models, these effects show that the "twisted" sector dominates the low-energy dynamics.

hep-th↗