Exploring the formation of spheroidal galaxies out to z ∼ 1.5 in GOODS

The formation of massive spheroidal galaxies is studied on a visually classified sample extracted from the Advanced Camera for Surveys/Hubble Space Telescope (ACS/HST) images of the Great Observatories Origins Deep Survey north and south fields, covering a total area of 360 arcmin . The sample size (910 galaxies brighter than i = 24) allows us to explore in detail the evolution over a wide range of redshifts (0.4 10 M galaxies by a factor of 2 between z = 1 and 0, in contrast with a factor of ∼50 for lower mass galaxies (10 <M / M <10 ). One-quarter of the whole sample of early types are photometrically classified as blue galaxies. On a volume-limited sample out to z <0.7, the average stellar mass of the blue ellipticals is 5 × 10 M compared to 4 × 10 M for red ellipticals. On a volume-limited subsample out to z = 1.4 probing the brightest galaxies (M <-21), we find the median redshift of blue and red early types: 1.10 and 0.85, respectively. Blue early types only amount to 4 per cent of this sample (compared to 26 per cent in the full sample). The intrinsic colour distribution correlates overall bluer colours with blue cores (positive radial gradients of colour), suggesting an inside-out process of formation. The redshift evolution of the observed colour gradients is incompatible with a significant variation in stellar age within each galaxy. The slope of the Kormendy relation in the subsample of massive galaxies does not change over 0.4 <z <1.4 and is compatible with z = 0 values. The 'zero-point' of the Kormendy relation (i.e. the surface brightness at a fixed half-light radius) is 1 mag fainter (in the B band) for the subsample of low-mass (M <3.5 × 10 M ) early types.Peer reviewe

SPIDER X - Environmental effects in central and satellite early-type galaxies through the stellar fossil record

A detailed analysis of how environment affects the star formation history of early-type galaxies (ETGs) is undertaken via high signal to noise ratio stacked spectra obtained from a sample of 20,977 ETGs (morphologically selected) from the SDSS-based SPIDER survey. Two major parameters are considered for the study: the central velocity dispersion (sigma), which relates to local drivers of star formation, and the mass of the host halo, which relates to environment-related effects. In addition, we separate the sample between centrals (the most massive galaxy in a halo) and satellites. We derive trends of age, metallicity, and [alpha/Fe] enhancement, with sigma. We confirm that the major driver of stellar population properties in ETGs is velocity dispersion, with a second-order effect associated to the central/satellite nature of the galaxy. No environmental dependence is detected for satellite ETGs, except at low sigma - where satellites in groups or in the outskirts of clusters tend to be younger than those in the central regions of clusters. In contrast, the trends for centrals show a significant dependence on halo mass. Central ETGs in groups (i.e. with a halo mass >10^12.5 M_Sun) have younger ages, lower [alpha/Fe], and higher internal reddening, than "isolated" systems (i.e. centrals residing in low-mass, <10^12.5 M_Sun, halos). Our findings imply that central ETGs in groups formed their stellar component over longer time scales than "isolated" centrals, mainly because of gas-rich interactions with their companion galaxies.Comment: 22 pages, 19 figures, accepted for publication in MNRA

Atmospheric neutrinos from charm

Using next-to-leading order perturbative QCD, we find that the charm contribution to the atmospheric lepton fluxes dominates over the conventional ones from pi and K decays for energies higher than 10^5 GeV. We also discuss theoretical uncertainties involved in the calculations and compare our results with previous evaluations.Comment: 5 pages, 1 figure, submitted to the Proceedings of the International Workshop on Particle Physics and the Early Universe (COSMO-98), ed. David Caldwell, Asilomar, Monterey, California, November 15-20, 199

Mapping a Homopolymer onto a Model Fluid

We describe a linear homopolymer using a Grand Canonical ensemble formalism, a statistical representation that is very convenient for formal manipulations. We investigate the properties of a system where only next neighbor interactions and an external, confining, field are present, and then show how a general pair interaction can be introduced perturbatively, making use of a Mayer expansion. Through a diagrammatic analysis, we shall show how constitutive equations derived for the polymeric system are equivalent to the Ornstein-Zernike and P.Y. equations for a simple fluid, and find the implications of such a mapping for the simple situation of Van der Waals mean field model for the fluid.Comment: 12 pages, 3 figure

Collapse of a semiflexible polymer in poor solvent

We investigate the dynamics and the pathways of the collapse of a single, semiflexible polymer in a poor solvent via 3-D Brownian Dynamics simulations. Earlier work indicates that the condensation of semiflexible polymers generically proceeds via a cascade through metastable racquet-shaped, long-lived intermediates towards the stable torus state. We investigate the rate of decay of uncollapsed states, analyze the preferential pathways of condensation, and describe likelihood and lifespan of the different metastable states. The simulation are performed with a bead-stiff spring model with excluded volume interaction and exponentially decaying attractive potential. The semiflexible chain collapse is studied as functions of the three relevant length scales of the phenomenon, i.e., the total chain length $L$, the persistence length $L_p$ and the condensation length $L_0 = \sqrt{k_B T L_p/u_0}$, where $u_0$ is a measure of the attractive potential per unit length. Two dimensionless ratios, $L/L_p$ and $L_0/L_p$, suffice to describe the decay rate of uncollapsed states, which appears to scale as $(L/L_p)^{1/3} (L_0/L_p)$. The condensation sequence is described in terms of the time series of the well separated energy levels associated with each metastable collapsed state. The collapsed states are described quantitatively through the spatial correlation of tangent vectors along the chain. We also compare the results obtained with a locally inextensible bead-rod chain and with a phantom bead-spring model. Finally, we show preliminary results on the effects of steady shear flow on the kinetics of collapse.Comment: 9 pages, 8 figure

Elevated cerebral spinal fluid biomarkers in children with mucopolysaccharidosis I-H.

Mucopolysaccharidosis (MPS) type-IH is a lysosomal storage disease that results from mutations in the IDUA gene causing the accumulation of glycosaminoglycans (GAGs). Historically, children with the severe phenotype, MPS-IH (Hurler syndrome) develop progressive neurodegeneration with death in the first decade due to cardio-pulmonary complications. New data suggest that inflammation may play a role in MPS pathophysiology. To date there is almost no information on the pathophysiologic changes within the cerebral spinal fluid (CSF) of these patients. We evaluated the CSF of 25 consecutive patients with MPS-IH. While CSF glucose and total protein were within the normal range, we found a significantly mean elevated CSF opening pressure at 24 cm H2O (range 14-37 cm H2O). We observed a 3-fold elevation in CSF heparan sulfate and a 3-8 fold increase in MPS-IH specific non-reducing ends, I0S0 and I0S6. Cytokine analyses in CSF of children with MPS-IH showed significantly elevated inflammatory markers including: MCP-1 SDF-1a, IL-Ra, MIP-1b, IL-8, and VEGF in comparison to unaffected children. This is the largest report of CSF characteristics in children with MPS-IH. Identification of key biomarkers may provide further insight into the inflammatory-mediated mechanisms related to MPS diseases and perhaps lead to improved targeted therapies

IMF and [Na/Fe] abundance ratios from optical and NIR Spectral Features in Early-type Galaxies

We present a joint analysis of the four most prominent sodium-sensitive features (NaD, NaI8190, NaI1.14, and NaI2.21), in the optical and Near-Infrared spectral range, of two nearby, massive (sigma~300km/s), early-type galaxies (named XSG1 and XSG2). Our analysis relies on deep VLT/X-Shooter long-slit spectra, along with newly developed stellar population models, allowing for [Na/Fe] variations, up to 1.2dex, over a wide range of age, total metallicity, and IMF slope. The new models show that the response of the Na-dependent spectral indices to [Na/Fe] is stronger when the IMF is bottom heavier. For the first time, we are able to match all four Na features in the central regions of massive early-type galaxies, finding an overabundance of [Na/Fe], in the range 0.5-0.7dex, and a bottom-heavy IMF. Therefore, individual abundance variations cannot be fully responsible for the trends of gravity-sensitive indices, strengthening the case towards a non-universal IMF. Given current limitations of theoretical atmosphere models, our [Na/Fe] estimates should be taken as upper limits. For XSG1, where line strengths are measured out to 0.8Re, the radial trend of [Na/Fe] is similar to [Mg/Fe] and [C/Fe], being constant out to 0.5Re, and decreasing by 0.2-0.3dex at 0.8Re, without any clear correlation with local metallicity. Such a result seems to be in contrast with the predicted increase of Na nucleosynthetic yields from AGB stars and TypeII SNe. For XSG1, the Na-inferred IMF radial profile is consistent, within the errors, with that derived from TiO features and the Wing-Ford band, presented in a recent paper.Comment: 22 pages, 8 figure, accepted for publication in MNRAS. The new Na-enhanced models will be available soon at http://miles.iac.es

The HI content of the recently discovered field dwarf galaxy APPLES1

We present observations in a search for neutral hydrogen associated with the recently detected field dwarf galaxy APPLES1, performed with the Parkes radiotelescope. The observed radio spectrum shows no evident (> 3sigma rms) line emission indicating an upper limit for the HI content of the galaxy of ~ 10E6 solar masses and providing an upper value for the M(HI)/L(B) ratio equal to 2.4 solar masses/solar luminosities. The low value of the HI content suggested by the observations, together with the galaxy optical morphology, might indicate that APPLES1 is a dwarf spheroidal. This indication is in contrast with the evidence of recent star formation, which is typical for dwarf irregular galaxies. This may suggest that APPLES1 belongs to the class of mixed dwarf irregular/spheroidal transition-type galaxies. We also conclude that the relatively low neutral gas mass in APPLES1 can be explained by an extended and inefficient star formation process, without the need for a dramatic event such as enhanced star formation or a past encounter with a massive galaxy or galaxy group.Comment: 5 pages including 2 figures, accepted for publication in A&A Main Journa