Photometric study of the IC 65 group of galaxies

We carry out a photometric study of a poor group of late-type galaxies around IC 65, with the aim: (a) to search for new dwarf members and to measure their photometric characteristics; (b) to search for possible effects of mutual interactions on the morphology and star-formation characteristics of luminous and faint group members; (c) to evaluate the evolutionary status of this particular group. We make use of our BRI CCD observations, DPOSS blue and red frames, and the 2MASS JHK frames. In addition, we use the HI imaging data, the far-infrared and radio data from the literature. Search for dwarf galaxies is made using the SExtractor software. Detailed surface photometry is performed with the MIDAS package. Four LSB galaxies were classified as probable dwarf members of the group and the BRI physical and model parameters were derived for the first time for all true and probable group members. Newly found dIrr galaxies around the IC 65 contain a number of H II regions, which show a range of ages and propagating star-formation. Mildly disturbed gaseous and/or stellar morphology is found in several group members. Various structural, dynamical, and star-forming characteristics let us conclude that the IC 65 group is a typical poor assembly of late-type galaxies at an early stage of its dynamical evolution with some evidence of intragroup (tidal) interactions.Comment: 21 pages, 16 figures, submitted to A&

Polarimetric imaging of interacting pairs

We present optical polarization maps of a sample of four interacting pairs at different phases of encounter, from nearly unperturbed galaxies to on-going mergers. Only the pair RR 24 shows a linear polarization pattern which extends in both galaxies for several kiloparsecs. The more perturbed member, RR 24b, is lineraly polarized up to the level of ~3%. No polarization is measured in the strongly perturbed late-type pair members of RR 23 and RR 99. Also, in the central part of the double nuclei shell galaxy ESO 2400100 there is no significant polarization. We use the ionized gas velocity field of RR 24 to interpret its linear polarization structure. In RR 24a the quite regular gas kinematics reflect the unperturbed spiral-like polarization structure. In RR 24b a strong velocity gradient in ionized gas could be associated with the polarization structure. We suggest that the large-scale magnetic field of the RR 24 pair members still plays a role in shaping the polarization pattern.Comment: 9 pages, 5 figures, accepted for publication in A

Small scale systems of galaxies I. Photometric and spectroscopic properties of members

This paper is the first of a series addressed to the investigation of galaxy formation/evolution in small scale systems of galaxies (SSSGs) which are located in low density cosmic environments. Our algorithm for SSSG selection includes galaxy systems of 2 or more galaxies lying within 1000 km/s and a 200 h_{100}^{-1} kpc radius volume. We present the analysis of the photometric and spectroscopic properties of 19 member galaxies belonging to a sample of 11 SSSGs. In the $\mu_e - r_e$ plane, early-type members may be considered "ordinary", not "bright" galaxies in the definition given by Capaccioli et al.(1992) with a significant fraction of galaxies having a disk or disky isophotes. We do not detect fine structure and signatures of recent interaction events in the early-type galaxy population, a picture also confirmed by the spectroscopy. At odd, there are several spiral members with open arm configurations as expected in interacting systems. At the same time, emission lines in the spectra of spiral members fall in the HII regions regime defined with diagnostic diagrams (Veilleux & Osterbrock 1987). None of the objects displays unambiguous indication of nuclear activity, although fourspiral nuclei could be ascribed to the class of Seyferts. The star formation rate seems enhanced over the average expected in spiral galaxies only for poorer SSSGs in particular pairs (<50 solar masses per year) but without being in the range of starburst systems.Comment: 24 pages, including 6 figures and 6 tables. Accepted for publication in A

Seyfert galaxies in UZC-Compact Groups

We present results concerning the occurrence of Seyfert galaxies in a new automatically selected sample of nearby Compact Groups of galaxies (UZC-CGs). Seventeen Seyferts are found, constituting ~3% of the UZC-CG galaxy population. CGs hosting and non-hosting a Seyfert member exhibit no significant differences, except that a relevant number of Sy2 is found in unusual CGs, all presenting large velocity dispersion (sigma > 400 km/s), many neighbours and a high number of ellipticals. We also find that the fraction of Seyferts in CGs is 3 times as large as that among UZC-single-galaxies, and results from an excess of Sy2s. CG-Seyferts are not more likely than other CG galaxies to present major interaction patterns, nor to display a bar. Our results indirectly support the minor-merging fueling mechanism.Comment: 12 pages, 5 figures, A&A, accepte

The 2MASS Redshift Survey - Description and Data Release

We present the results of the 2MASS Redshift Survey (2MRS), a ten-year project to map the full three-dimensional distribution of galaxies in the nearby Universe. The 2 Micron All-Sky Survey (2MASS) was completed in 2003 and its final data products, including an extended source catalog (XSC), are available on-line. The 2MASS XSC contains nearly a million galaxies with Ks <= 13.5 mag and is essentially complete and mostly unaffected by interstellar extinction and stellar confusion down to a galactic latitude of |b|=5 deg for bright galaxies. Near-infrared wavelengths are sensitive to the old stellar populations that dominate galaxy masses, making 2MASS an excellent starting point to study the distribution of matter in the nearby Universe. We selected a sample of 44,599 2MASS galaxies with Ks =5 deg (>= 8 deg towards the Galactic bulge) as the input catalog for our survey. We obtained spectroscopic observations for 11,000 galaxies and used previously-obtained velocities for the remainder of the sample to generate a redshift catalog that is 97.6% complete to well-defined limits and covers 91% of the sky. This provides an unprecedented census of galaxy (baryonic mass) concentrations within 300 Mpc. Earlier versions of our survey have been used in a number of publications that have studied the bulk motion of the Local Group, mapped the density and peculiar velocity fields out to 50 Mpc, detected galaxy groups, and estimated the values of several cosmological parameters. Additionally, we present morphological types for a nearly-complete sub-sample of 20,860 galaxies with Ks = 10 deg.Comment: Accepted for publication in The Astrophysical Journal Supplement Series. The 2MRS catalogs and a version of the paper with higher-resolution figures can be found at http://tdc-www.harvard.edu/2mrs

Cross-Cultural Evidence on Students' Perceptions of Experiential Learning

The experiential learning approach in higher education enables the effectiveness of courses and is particularly important for having a positive influence on students� engagement in the learning process. This is because it is the learning experience that students tend to assimilate in their quest to develop their knowledge-base. In order to find out how students from United States and Romania perceive the benefits of experiential learning techniques, we conducted a quantitative survey on convenience samples from two higher education institutions, one from Romania and the other from United States and analyzed the results by means of appropriate statistical tests. The results indicate that U.S. students get in contact with experiential learning methods more than the Romanian students, as the American education system represents a model of students-centered setting, where learning through experience is highly supported