The Quest for the Dominant Stellar Population in the Giant Elliptical NGC 5018

Newly obtained HST/WFPC2 images of the disturbed elliptical galaxy NGC 5018 show that the average amount of internal reddening due to the its complex ``dust web'' is as low as E(B-V)~0.02 within the IUE aperture, thus implying that its observed and intrinsic energy distributions do not differ significantly down to UV wavelengths. This, in turn, is quite relevant to the current debate on the age of its dominant stellar population.Comment: 2 pages, 1 figure. Proceedings of the conference "Galaxy Disks and Disk Galaxies", ASP Conference Series, eds. J.G. Funes, S.J. and E.M. Corsin

Galaxy Evolution in Local Group Analogs. I. A GALEX study of nearby groups

Understanding the astrophysical processes acting within galaxy groups and their effects on the evolution of the galaxy population is one of the crucial topic of modern cosmology, as almost 60% of galaxies in the Local Universe are found in groups. We imaged in the far (FUV 1539 A) and near ultraviolet (NUV 2316 A) with GALEX three nearby groups, namely LGG93, LGG127 and LGG225. We obtained the UV galaxy surface photometry and, for LGG225, the only group covered by the SDSS, the photometry in u, g, r, i, z bands. We discuss galaxy morphologies looking for interaction signatures and we analyze the SED of galaxies to infer their luminosity-weighted ages. The UV and optical photometry was also used to perform a kinematical and dynamical analysis of each group and to evaluate the stellar mass. A few member galaxies in LGG225 show a distorted UV morphology due to ongoing interactions. (FUV-NUV) colors suggest that spirals in LGG93 and LGG225 host stellar populations in their outskirts younger than that of M31 and M33 in the LG or with less extinction. The irregular interacting galaxy NGC3447A has a significantly younger stellar population (few Myr old) than the average of the other irregular galaxies in LGG225 suggesting that the encounter triggered star formation. The early-type members of LGG225, NGC3457 and NGC3522, have masses of the order of a few 10^9 Mo, comparable to the Local Group ellipticals. For the most massive spiral in LGG225, we estimate a stellar mass of ~4x10$^{10}$ Mo, comparable to M33 in the LG. Ages of stellar populations range from a few to ~7 Gyr for the galaxies in LGG225. The kinematical and dynamical analysis indicates that LGG127 and LGG225 are in a pre-virial collapse phase, i.e. still undergoing dynamical relaxation, while LGG93 is likely virialized. (Abridged)Comment: 20 pages, 13 figures, accepted for publication in Astronomy and Astrophysic

The mid-UV population of the nucleus and the bulk of the post-merger NGC 3610

The very center of NGC~3610, a clearly disturbed giant elliptical generally assumed to be a post-merger remnant, appears dominated in the mid-UV (2500-3200 A spectral region) by a stellar population markedly different from that dominating the bulk of its stellar body. I want here to make use of the mid-UV spectra of NGC~3610 as seen through tiny ($\sim$1") and large (10"$\times$20") apertures as a diagnostic population tool. I compare archive IUE/LWP large aperture and HST/FOS UV data of NGC 3610. The strength of mid-UV triplet (dominated by the turnoff population) shows a remarkable drop when switching from the galaxy central arcsec (FOS aperture) to an aperture size comparable to $\sim$0.5 r$_e$ (IUE). The sub-arsec (mid)-UV properties of this galaxy involved in a past merger reveal a central metal enrichment which left intact the bulk of its pre-existing population.Comment: 6 pages, 2 figures, accepted for publication in astronomy and Astrophysic

Viability analysis of using cellulose pulp recycled from cement sacks in the production of compressed earth blocks

This study concerns the development and analysis of the Kraftterra composite – raw earth stabilized with disperse fibers made with kraft paper from recycled cement sacks – for the production of CEBs and mortar for masonry infill elements. Its main goal is to define the behavior of small walls (prisms) of Kraftterra in relation to diagonal compression. The tests show that the prisms produced with Kraftterra CEBs and mortar show excellent bond strength between block and mortar. All the prisms tested presented fissure lines very close to the normal load line and the fissures occurred in the blocks and in the mortar in similar manner, without separation between these elements. The mortar produced with Kraftterra results in strong bonds between blocks and produces homogeneous construction elements with uniform performance, that is, with high monolithicity

Dissecting Kinematics and Stellar Populations of Counter-Rotating Galaxies with 2-Dimensional Spectroscopy

We present a spectral decomposition technique and its applications to a sample of galaxies hosting large-scale counter-rotating stellar disks. Our spectral decomposition technique allows to separate and measure the kinematics and the properties of the stellar populations of both the two counter-rotating disks in the observed galaxies at the same time. Our results provide new insights on the epoch and mechanism of formation of these galaxies.Comment: 4 pages, 3 figures. Contributed talk presented at the Conference "Multi-Spin galaxies", September 30 - October 3, 2013, INAF-Astronomical Observatory of Capodimonte, Naples, Italy. To be published in ASP Conf. Ser., Multi-Spin Galaxies, ed. E. Iodice & E. M. Corsini (San Francisco: ASP

KRAFTTERRA composite: Performance analysis of compressed earth blocks with and without cellulose pulp deriving from cement sacks recycling

This study presents part of the results of an experimental campaign on the mechanical behaviour of Kraftterra composite. This research was developed as a framework of collaboration between the University of Brasilia, in Brazil, and the University of Aveiro, in Portugal. The objective of this study involves the development and the performance evaluation of compressed earthen blocks for the construction incorporating recycled cement sacks. Research’s main goal is the hypothesis verification that the cellulose pulp that stem from cement sacks can be used to improve the characteristics, and particularly the mechanical properties, of the blocks with soil as raw material. This paper presents the Kraftterra mixture and production processes, as well as the performance analysis of compressed earth blocks – CEBs – produced with Kraftterra regarding the compressive strength

The UV window on counter rotating ETGs: insight from SPH simulations with chemo-photometric implementation

The Galaxy Evolution Explorer (GALEX) detected ultraviolet emission in about 50% of multi-spin early-type galaxies (ETGs), suggesting the occurrence of a recent rejuvenation episode connected to the formation of these kinematical features. With the aim at investigating the complex evolutionary scenario leading to the formation of counter rotating ETGs (CR-ETGs) we use our Smooth Particle Hydrodynamic (SPH) code with chemo-photometric implementation. We discuss here the UV evolutionary path of two CR-ETGs, NGC 3593 and NGC 5173, concurrently best fitting their global observed properties, i.e., morphology, dynamics, as well as their total B-band absolute magnitude and spectral energy distribution (SED) extended over three orders of magnitude in wavelength. These simulations correspond to our predictions about the target evolution which we follow in the color-magnitude diagram (CMD), near-UV (NUV) versus r-band absolute magnitude, as a powerful diagnostic tool to emphasize rejuvenation episodes.Comment: 7 pages, 3 figures, accepted for publication in ApS

Bimodality in low-luminosity E and S0 galaxies

Stellar population characteristics are presented for a sample of low-luminosity early-type galaxies (LLEs) in order to compare them with their more luminous counterparts. Long-slit spectra of a sample of 10 LLEs were taken with the ESO New Technology Telescope, selected for their low luminosities. Line strengths were measured on the Lick standard system. Lick indices for these LLEs were correlated with velocity dispersion (σ), alongside published data for a variety of Hubble types. The LLEs were found to fall below an extrapolation of the correlation for luminous ellipticals and were consistent with the locations of spiral bulges in plots of line strengths versus σ. Luminosity weighted average ages, metallicities and abundance ratios were estimated from χ2 fitting of 19 Lick indices to predictions from simple stellar population models. The LLEs appear younger than luminous ellipticals and of comparable ages to spiral bulges. These LLEs show a bimodal metallicity distribution, consisting of a low-metallicity group (possibly misclassified dwarf spheroidal galaxies) and a high-metallicity group (similar to spiral bulges). Finally, they have low α-element to iron peak abundance ratios indicative of slow, extended star formation