Robust Neutrino Constraints by Combining Low Redshift Observations with the CMB (2009)
Reid, Beth A., Verde, Licia, Jimenez, Raul, Mena, Olga
We illustrate how recently improved low-redshift cosmological measurements can tighten constraints on neutrino properties. In particular we examine the impact of the assumed cosmological model on the...
The recent weak lensing measurement of the dark matter mass of the high-redshift galaxy cluster XMMUJ2235.3-2557 of (8.5 +- 1.7) x 10^{14} Msun at z=1.4, indicates that, if the cluster is assumed to...
Cosmic Chronometers: Constraining the Equation of State of Dark Energy. I: H(z) Measurements (2009)
Stern, Daniel, Jimenez, Raul, Verde, Licia, Kamionkowski, Marc, Stanford, S. Adam
We present new determinations of the cosmic expansion history from red-envelope galaxies. We have obtained for this purpose high-quality spectra with the Keck-LRIS spectrograph of red-envelope...
Stern, Daniel, Jimenez, Raul, Verde, Licia, Stanford, S. Adam, Kamionkowski, Marc
We present a spectroscopic catalog of (mostly) red galaxies in 24 galaxy clusters in the redshift range 0.17 < z < 0.92 obtained with the LRIS instrument on the Keck I telescope. Here we describe the...
Jimenez, Raul, Slosar, Anze, Verde, Licia, Bamford, Steven, Lintott, Chris, Schawinski, Kevin, ...
We report on the finding of a correlation between galaxies' past star formation activity and the degree to which neighbouring galaxies rotation axes are aligned. This is obtained by cross-correlating...
Tojeiro, Rita, Wilkins, Stephen, Heavens, Alan F., Panter, Ben, Jimenez, Raul
We applied the VESPA algorithm to the Sloan Digital Sky Survey final data release of the Main Galaxies and Luminous Red Galaxies samples. The result is a catalogue of stellar masses, detailed star...
First lensing measurements of SZ-discovered clusters (2009)
McInnes, Rachel N., Menanteau, Felipe, Heavens, Alan F., Hughes, John P., Jimenez, Raul, Massey, Richard, ...
We present the first lensing mass measurements of Sunyaev-Zel'dovich (SZ) selected clusters. Using optical imaging from the Southern Cosmology Survey (SCS), we present weak lensing masses for three...
Consistency among distance measurements: transparency, BAO scale and accelerated expansion (2009)
Avgoustidis, A., Verde, Licia, Jimenez, Raul
We explore consistency among different distance measures, including Supernovae Type Ia data, measurements of the Hubble parameter, and determination of the Baryon acoustic oscillation scale. We...
The void abundance with non-gaussian primordial perturbations (2009)
Kamionkowski, Marc, Verde, Licia, Jimenez, Raul
We use a Press-Schechter-like calculation to study how the abundance of voids changes in models with non-Gaussian initial conditions. While a positive skewness increases the cluster abundance, a...
Menanteau, Felipe, Hughes, John P., Jimenez, Raul, Hernandez-Monteagudo, Carlos, Verde, Licia, Kosowsky, Arthur, ...
Photo-z optimization for measurements of the BAO radial direction (2008)
Roig, Daniel, Verde, Licia, Miralda-Escude, Jordi, Jimenez, Raul, Pena-Garay, Carlos
Baryon Acoustic Oscillations (BAO) in the radial direction offer a method to directly measure the Universe expansion history, and to set limits to space curvature when combined to the angular BAO...
Southern Cosmology Survey III: QSO's from Combined GALEX and Optical Photometry (2008)
Jimenez, Raul, Spergel, David N., Niemack, Michael D., Menanteau, Felipe, Hughes, John P., Verde, Licia, ...
We present catalogs of QSO candidates selected using photometry from GALEX combined with SDSS in the Stripe 82 region and Blanco Cosmology Survey (BCS) near declination -55 degrees. The SDSS region...
Physical Classification of Galaxies with MOPED/VESPA (2008)
Jimenez, Raul, Heavens, Alan F., Panter, Ben, Tojeiro, Rita
The availability of high-quality spectra for a large number of galaxies in the SDSS survey allows for a more sophisticated extraction of information about their stellar populations than, e.g., the...
Revisiting the effect of H2, HD and LiH molecules in the cooling of primordial gas (2008)
Prieto, Joaquin P., Infante, Leopoldo, Jimenez, Raul
We use a non-equilibrium chemical network to revisit and study the effect of H_{2}, HD and LiH molecular cooling on a primordial element of gas. We solve both the thermal and chemical equations for a...
The Void Abundance with Non-Gaussian Primordial Perturbations (2008)
Kamionkowski, Marc, Verde, Licia, Jimenez, Raul
We use a Press-Schechter-like calculation to study how the abundance of voids changes in models with non-Gaussian initial conditions. While a positive skewness increases the cluster abundance, a...
Menanteau, Felipe, Hughes, John P., Jimenez, Raul, Hernandez-Monteagudo, Carlos, Verde, Licia, Kosowsky, Arthur, ...
We present first results from the Southern Cosmology Survey, a new multiwavelength survey of the southern sky coordinated with the Atacama Cosmology Telescope (ACT), a recently commissioned...
Improved Cosmological Parameter Constraints from CMB and H(z) Data (2008)
Figueroa, Daniel G., Verde, Licia, Jimenez, Raul
We discuss the cosmological degeneracy between the Hubble parameter H(z), the age of the universe and cosmological parameters describing simple variations from the minimal LCDM model. We show that...
The Cosmic Evolution of Metallicity from the SDSS Fossil Record (2008)
Panter, Benjamin, Jimenez, Raul, Heavens, Alan F., Charlot, Stephane
We present the time evolution of the stellar metallicity for SDSS galaxies, a sample that spans five orders of magnitude in stellar mass (10^7 - 10^{12} Msun). Assuming the BC03 stellar population...
Niemack, Michael D., Jimenez, Raul, Verde, Licia, Menanteau, Felipe, Panter, Ben, Spergel, David
Four large-area Sunyaev-Zeldovich (SZ) experiments -- APEX-SZ, SPT, ACT, and Planck -- promise to detect clusters of galaxies through the distortion of Cosmic Microwave Background photons by hot (>...
The role of spin in the formation and evolution of galaxies (2008)
Berta, Zachory K., Jimenez, Raul, Heavens, Alan F., Panter, Ben
Using the SDSS spectroscopic sample, we estimate the dark matter halo spin parameter lambda for ~53,000 disk galaxies for which MOPED star formation histories are available. We investigate the...
The scale dependence of mass assembly in galaxies (2008)
Mateus, Abilio, Jimenez, Raul, Gaztanaga, Enrique
We compare the results of the mark correlation analysis of galaxies in a sample from the Sloan Digital Sky Survey and from two galaxy catalogs obtained by semi-analytical galaxy formation models...
Topology from Cosmology (2007)
Balasubramanian, Vijay, Berglund, Per, Jimenez, Raul, Simon, Joan, Verde, Licia
We show that cosmological observables can constrain the topology of the compact additional dimensions predicted by string theory. To do this, we develop a general strategy for relating cosmological...
Ages of Globular Clusters: A New Approach (2007)
Raul Jimenez, Uffe G. J��rgensen, James Macdonald
We have applied a new method to analyze the horizontal branch (HB) morphology in relation to the distribution of stars near the red giant branch (RGB) tip for the globular clusters M22, M5, M68,...
Hernandez-Monteagudo, Carlos, Haiman, Zoltan, Verde, Licia, Jimenez, Raul
At the epoch of reionization, when the high-redshift inter-galactic medium (IGM) is being enriched with metals, the 63.2 micron fine structure line of OI is pumped by the ~ 1300 AA soft UV background...
The Cosmic Neutrino Background and the Age of the Universe (2007)
De Bernardis, Francesco, Melchiorri, Alessandro, Verde, Licia, Jimenez, Raul
We discuss the cosmological degeneracy between the age of the Universe, the Hubble parameter and the effective number of relativistic particles N_eff. We show that independent determinations of the...
Evidence for short-lived SN Ia progenitors (2007)
Aubourg, Eric, Tojeiro, Rita, Jimenez, Raul, Heavens, Alan F., Strauss, Michael A., Spergel, David N.
We use the VESPA algorithm and spectra from the Sloan Digital Sky Survey to investigate the star formation history of the host galaxies of 257 Type Ia supernovae. We find 5$\sigma$ evidence for a...
Jimenez, Raul, Lugo, Haydee, Cuesta, Jose A., Sanchez, Angel
We study the problem of the emergence of cooperation in the spatial Prisoner's Dilemma. The pioneering work by Nowak and May showed that large initial populations of cooperators can survive and...
The Kinetic Sunyaev-Zel'dovich Effect Due to the Electrons of Our Galaxy (2007)
Hajian, Amir, Hernandez-Monteagudo, Carlos, Jimenez, Raul, Spergel, David, Verde, Licia
We compute the effect of local electrons on the CMB temperature anisotropies. The number density and distribution of free electrons in our Galaxy has been accurately measured from pulsar dispersion...
Recovering galaxy star formation and metallicity histories from spectra using VESPA (2007)
Tojeiro, Rita, Heavens, Alan F., Jimenez, Raul, Panter, Ben
We introduce VErsatile SPectral Analysis (VESPA): a new method which aims to recover robust star formation and metallicity histories from galactic spectra. VESPA uses the full spectral range to...
The Helium abundance and Delta Y / Delta Z in Lower Main Sequence stars (2007)
Casagrande, Luca, Flynn, Chris, Portinari, Laura, Girardi, Leo, Jimenez, Raul
We use nearby K dwarf stars to measure the helium-to-metal enrichment ratio, a diagnostic of the chemical history of the Solar Neighbourhood. Our sample of K dwarfs has homogeneously determined...
The ages metallicities, and star formation histories of early-type galaxies in the SDSS (2007)
Jimenez, Raul, Bernardi, Mariangela, Haiman, Zoltan, Panter, Ben, Heavens, Alan F.
Oxygen Pumping: Mapping the Reionization Epoch with the CMB (2006)
Hernandez-Monteagudo, Carlos, Haiman, Zoltan, Jimenez, Raul, Verde, Licia
We consider the pumping of the $63.2 \mu$m fine structure line of neutral OI in the high--redshift intergalactic medium (IGM), in analogy with the Wouthuysen--Field effect for the 21cm line of cosmic...
The ages, metallicities and star formation histories of early-type galaxies in SDSS (2006)
Jimenez, Raul, Bernardi, Mariangela, Haiman, Zoltan, Panter, Ben, Heavens, Alan F.
We use the spectra of ~ 22,000 early-type galaxies, selected from the Sloan Digital Sky Survey, to infer the ages, metallicities and star formation histories of these galaxies. We find clear evidence...
Haiman, Zoltan, Jimenez, Raul, Bernardi, Mariangela
We use the spectra of 22,000 nearby early-type galaxies from the Sloan Digital Sky Survey (SDSS) to determine the age distribution of these galaxies as a function of their velocity dispersion sigma_v...
The star formation histories of galaxies in the Sloan Digital Sky Survey (2006)
Panter, Ben, Jimenez, Raul, Heavens, Alan F., Charlot, Stephane
We present the results of a MOPED analysis of ~3 x 10^5 galaxy spectra from the Sloan Digital Sky Survey Data Release Three (SDSS DR3), with a number of improvements in data, modelling and analysis...
The thermal Sunyaev-Zel'dovich Signature of Baryons in the Local Universe (2006)
Hernandez-Monteagudo, Carlos, Trac, Hy, Jimenez, Raul, Verde, Licia
Using cosmological hydrodynamical simulations, we investigate the prospects of the thermal Sunyaev-Zel'dovich (tSZ) effect to detect the missing baryons in the local universe. We find that at least...
The star-formation histories of elliptical galaxies across the fundamental plane (2006)
Nolan, Louisa A., Dunlop, J. S., Panter, B., Jimenez, Raul, Heavens, A. F., Smith, G.
We present the first results from a study designed to test whether, given high-quality spectrophotometry spanning the mid-UV--optical wavelength regime, it is possible to distinguish the metal...
Using cosmology to constrain the topology of hidden dimensions (2006)
Simon, Joan, Jimenez, Raul, Verde, Licia, Berglund, Per, Balasubramanian, Vijay
A four-dimensional universe, arising from a flux compactification of Type IIB string theory, contains scalar fields with a potential determined by topological and geometric parameters of the internal...
Environment and the cosmic evolution of star formation (2006)
Sheth, Ravi K., Jimenez, Raul, Panter, Ben, Heavens, Alan
We present a mark correlation analysis of the galaxies in the Sloan Digital Sky Survey using weights provided by MOPED. The large size of the sample permits statistically significant statements about...
Tomography of the Reionization Epoch with Multifrequency CMB Observations (2006)
Hernandez-Monteagudo, Carlos, Verde, Licia, Jimenez, Raul
We study the constraints that future multifrequency Cosmic Microwave Background (CMB) experiments will be able to set on the metal enrichment history of the Inter Galactic Medium at the epoch of...
Significant primordial star formation at redshifts z ~ 3-4 (2006)
Four recent observational results have challenged our understanding of high--redshift galaxies, as they require the presence of far more ultraviolet photons than should be emitted by normal stellar...
Model Atmospheres for Irradiated Giant Stars: Implications for the Galactic Center (2006)
Jimenez, Raul, Da Silva, Juliana P., Oh, S. Peng, Jorgensen, Uffe G., Merritt, David
Irradiation of a stellar atmosphere by an external source (e.g. an AGN) changes its structure and therefore its spectrum. Using a state-of-the-art stellar atmosphere code, we calculate the infrared...
Stacking weak lensing signals of SZ clusters to constrain cluster physics (2006)
Sealfon, Carolyn, Verde, Licia, Jimenez, Raul
We show how to place constraints on cluster physics by stacking the weak lensing signals from multiple clusters found through the Sunyaev-Zeldovich (SZ) effect. For a survey that covers about 200 sq....
Environment and the cosmic evolution of star formation (2006)
Sheth, Ravi K., Jimenez, Raul, Panter, Ben, Heavens, Alan F.
Hernandez-Monteagudo, C., Verde, L., Jimenez, Raul, Spergel, D. N.
In the context of a cosmological study of the bulk flows in the Universe, we present a detailed study of the statistical properties of the kinematic Sunyaev-Zel'dovich (kSZ) effect. We first compute...
Smoothing spline primordial power spectrum reconstruction (2005)
Sealfon, Carolyn, Verde, Licia, Jimenez, Raul
We reconstruct the shape of the primordial power spectrum (PPS) using a smoothing spline. Our adapted smoothing spline technique provides a complementary method to existing efforts to search for...
Considerations in optimizing CMB polarization experiments to constrain inflationary physics (2005)
Verde, Licia, Peiris, Hiranya, Jimenez, Raul
We quantify the limiting factors in optimizing current-technology cosmic microwave background (CMB) polarization experiments in order to learn about inflationary physics. We consider space-based,...
Fast identification of transits from light-curves (2005)
Protopapas, Pavlos, Jimenez, Raul, Alcock, Charles
We present an algorithm that allows fast and efficient detection of transits, including planetary transits, from light-curves. The method is based on building an ensemble of fiducial models and...
Constraints on the redshift dependence of the dark energy potential (2004)
Simon, Joan, Verde, Licia, Jimenez, Raul
We develop a formalism to characterize the redshift evolution of the dark energy potential. Our formalism makes use of quantities similar to the Horizon-flow parameters in inflation and is general...
The Mass Function of the Stellar Component of Galaxies in the Sloan Digital Sky Survey (2004)
Panter, Ben, Heavens, Alan, Jimenez, Raul
Using the MOPED algorithm we determine non-parametrically the Stellar Mass Function of 96,545 galaxies from the Sloan Digital Sky Survey data release one. By using the reconstructed spectrum due to...
Jimenez, Raul, Verde, Licia, Peiris, Hiranya, Kosowsky, Arthur
We improve the algorithm of Kosowsky, Milosavljevic, and Jimenez (2002) for computing power spectra of the cosmic microwave background. The present algorithm computes not only the temperature power...
Limits on deviations from the inverse-square law on megaparsec scales (2004)
Sealfon, Carolyn, Verde, Licia, Jimenez, Raul
We present an attempt to constrain deviations from the gravitational inverse-square law on large-scale structure scales. A perturbed law modifies the Poisson equation, which implies a scale-dependent...
Jimenez, Raul, Panter, Benjamin, Heavens, Alan, Verde, Licia
Using the spectroscopic sample of the SDSS DR1 we measure how gas was transformed into stars as a function of time and stellar mass: the baryonic conversion tree (BCT). There is a clear correlation...
The Complete Star Formation History of the Universe (2004)
Heavens, Alan, Panter, Benjamin, Jimenez, Raul, Dunlop, James
The determination of the star-formation history of the Universe is a key goal of modern cosmology, as it is crucial to our understanding of how structure in the Universe forms and evolves. A picture...
Jimenez, Raul, MacDonald, James, Dunlop, James, Padoan, Paolo, Peacock, John
We present a new set of stellar interior and synthesis models for predicting the integrated emission from stellar populations in star clusters and galaxies of arbitrary age and metallicity. This work...
Padoan, Paolo, Jimenez, Raul, Juvela, Mika, Nordlund, Aake
The magnetic field strength in molecular clouds is a fundamental quantity for theories of star formation. It is estimated by Zeeman splitting measurements in a few dense molecular cores, but its...
The value of the equation of state of dark energy (2003)
From recent CMB and Large Scale Structure observations the value of the equation of state of dark energy, assuming it to be constant in time, is constrained to be -1.3
The cosmic production of Helium (2003)
Jimenez, Raul, Flynn, Chris, MacDonald, James, Gibson, Brad K.
We estimate the cosmic production rate of helium relative to metals ($\Delta Y/\Delta Z$) using K dwarf stars in the Hipparcos catalog with accurate spectroscopic metallicities. The best fitting...
Jimenez, Raul, Verde, Licia, Treu, Tommaso, Stern, Daniel
We place tight constraints on the redshift-averaged, effective value of the equation of state of dark energy, w, using only the absolute ages of Galactic stars and the observed position of the first...
Structure Function Scaling in Compressible Super-Alfvenic MHD Turbulence (2003)
Padoan, Paolo, Jimenez, Raul, Nordlund, Aake, Boldyrev, Stanislav
Supersonic turbulent flows of magnetized gas are believed to play an important role in the dynamics of star-forming clouds in galaxies. Understanding statistical properties of such flows is crucial...
The cosmic production of helium (2003)
Flynn, Chris, Gibson, Brad K., Jimenez, Raul, MacDonald, James
Abstract not available.
The cosmic production of helium (2003)
Flynn, Chris, Gibson, Brad K., Jimenez, Raul, MacDonald, James
Abstract not available.
The cosmic production of helium (2003)
Flynn, Chris, Gibson, Brad K., Jimenez, Raul, MacDonald, James
Abstract not available.
The cosmic production of helium (2003)
Flynn, Chris, Gibson, Brad K., Jimenez, Raul, MacDonald, James
Abstract not available.
The cosmic production of helium (2003)
Jimenez, Raul, Flynn, Chris, MacDonald, James, Gibson, Brad K.
We estimate the cosmic production rate of helium relative to metals (ΔY/ΔZ) using K dwarf stars in the Hipparcos catalog with accurate spectroscopic metallicities. The best fitting value is ΔY/ΔZ...
Star Formation and Metallicity History of the SDSS galaxy survey: unlocking the fossil record (2002)
Panter, Benjamin, Heavens, Alan F., Jimenez, Raul
Using MOPED we determine non-parametrically the star-formation and metallicity history of over 37,000 high-quality galaxy spectra from the Sloan Digital Sky Survey (SDSS) early data release. We use...
Efficient Cosmological Parameter Estimation from Microwave Background Anisotropies (2002)
Kosowsky, Arthur, Milosavljevic, Milos, Jimenez, Raul
We revisit the issue of cosmological parameter estimation in light of current and upcoming high-precision measurements of the cosmic microwave background power spectrum. Physical quantities which...
Dark matter spikes and annihilation radiation from the galactic center (2002)
Merritt, David, Milosavljevic, Milos, Verde, Licia, Jimenez, Raul
Also archived in: arXiv: astro-ph/0201376 v3 9 May 2002
Dark matter spikes and annihilation radiation from the galactic center (2002)
Merritt, David, Milosavljevic, Milos, Verde, Licia, Jimenez, Raul
Also archived in: arXiv: astro-ph/0201376 v3 9 May 2002
Luminosity-metallicity relation for stars on the lower main sequence (2002)
Kotoneva, Eira, Flynn, Chris, Jimenez, Raul
We present a comparison of the predictions of stellar models with the luminosity of the lower main sequence ($5.5 < M_V < 7.3$) using K dwarfs in the Hipparcos catalog. The parallaxes of our...
The abundance of dark galaxies (2002)
Verde, Licia, Oh, S. Peng, Jimenez, Raul
We show that gas in a large fraction of low mass dark matter halos may form Toomre stable disks, if angular momentum is conserved when the gas contracts. Such halos would be stable to star formation...
Dark Matter Spikes and Annihilation Radiation from the Galactic Center (2002)
Merritt, David, Milosavljevic, Milos, Verde, Licia, Jimenez, Raul
The annihilation rate of weakly interacting cold dark matter particles at the galactic center could be greatly enhanced by the growth of a density spike around the central supermassive black hole...
Dark halo properties from rotation curves (2002)
Jimenez, Raul, Verde, Licia, Oh, S. Peng
We study a large set of high spatial resolution optical rotation curves of galaxies with the goal of determining the model parameters for a disk embedded within a CDM halo that we model either with a...
Luminosity-metallicity relation for stars on the lower main sequence (2002)
Flynn, Chris, Jimenez, Raul, Kotoneva, Eira
Abstract not available.
Luminosity-metallicity relation for stars on the lower main sequence (2002)
Flynn, Chris, Jimenez, Raul, Kotoneva, Eira
Abstract not available.
Luminosity-metallicity relation for stars on the lower main sequence (2002)
Flynn, Chris, Jimenez, Raul, Kotoneva, Eira
Abstract not available.
Luminosity-metallicity relation for stars on the lower main sequence (2002)
Flynn, Chris, Jimenez, Raul, Kotoneva, Eira
Abstract not available.
Luminosity-metallicity relation for stars on the lower main sequence (2002)
Flynn, Chris, Jimenez, Raul, Kotoneva, Eira
Abstract not available.
The Epoch of Galaxy Formation (2001)
I present a biased review of when the epoch of formation of galaxies (both disks and ellipticals) maybe took place. I base my arguments in simple (mostly) analytic models that have been recently...
The Origin of Blue Cores in Hubble Deep Fields E/S0 galaxies (2001)
Menanteau, Felipe, Jimenez, Raul, Matteucci, Francesca
In this letter we address the problem of the origin of blue cores and inverse color gradients in early-type galaxies reported in the Hubble Deep Field North and South (HDFs) by Menanteau, Abraham &...
Constraining Cosmological Parameters Based on Relative Galaxy Ages (2001)
We propose to use relative galaxy ages as a means of constraining cosmological parameters. By measuring the age difference between two ensembles of old galaxies at somewhat different redshifts, one...
F stars, metallicity, and the ages of red galaxies at z > 1 (2001)
Nolan, Louisa A., Dunlop, James S., Jimenez, Raul, Heavens, Alan F.
We explore whether the rest-frame near-UV spectral region, observable in high-redshift galaxies via optical spectroscopy, contains sufficient information to allow the degeneracy between age and...
Energetics of Gamma Ray Bursts (2001)
Jimenez, Raul, Band, David, Piran, Tsvi
We determine the distribution of total energy emitted by gamma-ray bursts for bursts with fluences and distance information. Our core sample consists of eight bursts with BATSE spectra and...
Galactosynthesis Predictions at High Redshift (2001)
Buchalter, Ari, Jimenez, Raul, Kamionkowski, Marc
We predict the Tully-Fisher (TF) and surface-brightness--magnitude relation for disk galaxies at z=3 and discuss the origin of these scaling relations and their scatter. We show that the variation of...
Recovering Physical Parameters from Galaxy Spectra Using MOPED (2001)
Reichardt, Christian, Jimenez, Raul, Heavens, Alan
We derive physical parameters of galaxies from their observed spectrum, using MOPED, the optimized data compression algorithm of Heavens, Jimenez & Lahav 2000. Here we concentrate on parametrising...
Tests for primordial non-Gaussianity (2000)
Verde, Licia, Jimenez, Raul, Kamionkowski, Marc, Matarrese, Sabino
We investigate the relative sensitivities of several tests for deviations from Gaussianity in the primordial distribution of density perturbations. We consider models for non-Gaussianity that mimic...
I review the statistical techniques needed to extract information about physical parameters of galaxies from their observed spectra. This is important given the sheer size of the next generation of...
Where are the absorbers towards Q2302+029? (2000)
Bowen, David V., Jimenez, Raul, Jenkins, Edward B., Pettini, Max
We present images and spectroscopy of objects close to the sightline of Q2302+029 in order to search for galaxies responsible for the remarkable z=0.7 high-ionization absorption line system found by...
Galactosynthesis: Halo Histories, Star Formation, and Disks (2000)
Buchalter, Ari, Jimenez, Raul, Kamionkowski, Marc
We investigate the effects of a variety of ingredients that must enter into a realistic model for disk-galaxy formation, focusing primarily on the Tully-Fisher (TF) relation and its scatter in...
The Sun, stellar-population models, and the age estimation of high-redshift galaxies (2000)
Nolan, Louisa A., Dunlop, James S., Jimenez, Raul
Given sufficiently deep optical spectroscopy, the age estimation of high-redshif t ($z > 1$) galaxies has been claimed to be a relatively robust process (e.g. Dunlop et al. 1996) due to the fact...
The abundance of high-redshift objects as a probe of non-Gaussian initial conditions (2000)
Matarrese, Sabino, Verde, Licia, Jimenez, Raul
The observed abundance of high-redshift galaxies and clusters contains precious information about the properties of the initial perturbations. We present a method to compute analytically the number...
Massive Lossless Data Compression and Multiple Parameter Estimation from Galaxy Spectra (1999)
Heavens, Alan, Jimenez, Raul, Lahav, Ofer
We present a method for radical linear compression of datasets where the data are dependent on some number $M$ of parameters. We show that, if the noise in the data is independent of the parameters,...
Primordial Proto-Galaxies (1999)
Padoan, Paolo, Jimenez, Raul, Dunlop, James
The first stars to form in protogalaxies must have primordial chemical composition. We refer to a protogalaxy that is forming stars of primordial composition, or very low metallicity ($Z\le 0.01...
Proto-Galactic Starbursts at High Redshift (1999)
Jimenez, Raul, Padoan, Paolo, Dunlop, James, Bowen, David, Juvela, Mika, Matteucci, Francesca
We have computed the evolving ultraviolet-millimeter spectral energy distribution (SED) produced by proto-galactic starbursts at high redshift, incorporating the chemical evolution of the...
Overmerging and M/L ratios in phenomenological galaxy formation models (1999)
Van Kampen, Eelco, Jimenez, Raul, Peacock, John A.
We show that the discrepancy between the Tully-Fisher relation and the luminosity function predicted by most phenomenological galaxy formation models is mainly due to overmerging of galaxy haloes. We...
Premature dismissal of high-redshift elliptical galaxies (1998)
Jimenez, Raul, Friaca, Amancio, Dunlop, James, Terlevich, Roberto, Peacock, John, Nolan, Louisa
It has recently been argued that single-collapse high-redshift models for elliptical galaxy formation can be rejected because they predict large numbers of very red galaxies at intermediate redshifts...
On the origin of Damped Lyman-alpha systems: a case for LSB galaxies? (1998)
Jimenez, Raul, Bowen, David V., Matteucci, Francesca
We use a model of galaxy disk formation to explore the metallicities, dust content, and neutral-gas mass density of damped Lyman-$\alpha$ (D\lya) absorbers. We find that the [Zn/H] abundance...
Galaxy Formation and Evolution: Low Surface Brightness Galaxies (1998)
Jimenez, Raul, Padoan, Paolo, Matteucci, Francesca, Heavens, Alan
We investigate in detail the hypothesis that low surface brightness galaxies (LSB) differ from ordinary galaxies simply because they form in halos with large spin parameters. We compute star...
Hipparcos and the Age of the Galactic Disc (1997)
We have used the Hipparcos satellite colour magnitude diagram to determine the age of the Galactic disc. We first measure the metallicities of Hipparcos giants using DDO photometry (H{\o}g & Flynn...
Dark galaxies, spin bias and gravitational lenses (1997)
Jimenez, Raul, Heavens, A. F., Hawkins, M. R. S., Padoan, P.
Gravitational lensing studies suggest that the Universe may contain a population of dark galaxies; we investigate this intriguing possibility and propose a mechanism to explain their nature. In this...
LBDS 53W091: An Old red Galaxy at z=1.552 (1997)
Spinrad, Hyron, Dey, Arjun, Stern, Daniel, Dunlop, James, Peacock, John, Jimenez, Raul, ...
The weak radio source LBDS 53W091 is associated with a very faint (R approx. 24.5) red (R-K approx. 5.8) galaxy. Long spectroscopic integrations with the W. M. Keck telescope have provided an...
The Age of the Universe (1997)
In this article I review the main methods for determining the age of the Universe. I describe how to determine the age of the oldest known systems at z=0, the system of galactic globular clusters,...
Are Low Surface Brightness Discs Young? (1996)
Padoan, Paolo, Jimenez, Raul, Antonuccio-Delogu, Vincenzo
We reconsider the problem of the age of the stellar discs of late-type Low Surface Brightness (LSB) galaxies by making use of a new IMF recently derived from numerical fluid dynamical simulations...
On star formation in primordial protoglobular clouds (1996)
Padoan, Paolo, Jimenez, Raul, Jones, Bernard
Using a new physical model for star formation (Padoan 1995) we have tested the possibility that globular clusters (GCs) are formed from primordial mass fluctuations, whose mass scale ($10^8$ - $10^9$...
Ages of globular clusters: breaking the age-distance degeneracy with the luminosity function (1996)
We extend our previous method to determine globular cluster ages using the luminosity function (Jimenez \& Padoan 1996). We show that the luminosity function depends on both age and distance modulus...
A new method to determine Globular Cluster ages (1996)
We present a new method to compute stellar ages in Globular Clusters (GC) that is ten times more precise than the traditional isochrone fitting procedure. The method relies on accurate stellar...
We review two new methods to determine the age of globular clusters (GCs). These two methods are more accurate than the classical isochrone fitting technique. The first method is based on the...
We review two new methods to determine the age of globular clusters (GCs). These two methods are more accurate than the classical isochrone fitting technique. The first method is based on the...
Resistance to learning and the evolution of cooperation
Raul Jimenez, Haydee Lugo, Maxi San Miguel
In many evolutionary algorithms, crossover is the main operator used in generating new individuals from old ones. However, the usual mechanism for generating offsprings in spatially structured...