The Fundamental Properties of Dwarf Elliptical Galaxies in Clusters

We present preliminary results of an extensive study of the fundamental properties of dwarf elliptical galaxies (dEs) in the Coma cluster. Our study will combine HST surface photometry with ground-based UBRIJK photometry and optical spectroscopy. The combined data set will be used to investigate the intrinsic correlations among global parameters in cluster dEs, including the Fundamental Plane, the color-magnitude relation, the Faber-Jackson and Kormendy relation, and velocity dispersion versus line strength indices. These empirical correlations have provided important constraints to theoretical models of galaxy formation and evolution for "normal" elliptical galaxies. Although dEs are the most abundant galaxy population in clusters their properties remain, however, largely unknown. Our study aims to provide an essential reference for testing current theories on the formation and evolution of dEs in clusters, and understanding their relation to more massive elliptical galaxies.Comment: 10 pages. To appear in "Star Formation through Time", 2003, ASP Conf. Ser. ed. Perez, Gonzalez Delgado, Tenorio-Tagl

Advanced Topics in Emergency Medicine: Curriculum Development and Initial Evaluation

<p>Background: Emergency medicine (EM) is a young specialty and only recently has a recommended medical student curriculum been developed. Currently, many schools do not require students to complete a mandatory clerkship in EM, and if one is required, it is typically an overview of the specialty.</p> <p>Objectives: We developed a 10-month longitudinal elective to teach subject matter and skills in EM to fourth-year medical students interested in the specialty. Our goal was producing EM residents with the knowledge and skills to excel at the onset of their residency. We hoped to prove that students participating in this rigorous 10-month longitudinal EM elective would feel well prepared for residency.</p> <p>Methods: We studied the program with an end-of-the-year, Internet-based, comprehensive course evaluation completed by each participant of the first 2 years of the course. Graduates rated each of the course components by using a 5-point Likert format from ‘‘strongly disagree’’ to ‘‘strongly agree,’’ either in terms of whether the component was beneficial to them or whether the course expectations were appropriate, or their perceptions related to the course.</p> <p>Results: Graduates of this elective have reported feeling well prepared to start residency. The resident-led teaching shifts, Advanced Pediatric Life Support certification, Grand Rounds presentations, Advanced Cardiovascular Life Support proficiency testing, and ultrasound component, were found to be beneficial by all students.</p> <p>Conclusions: Our faculty believes that participating students will be better prepared for an EM residency than those students just completing a 1-month clerkship. Our data, although limited, lead us to believe that a longitudinal, immersion-type experience assists fourth-year medical students in preparation for residency. [West J Emerg Med. 2011;12(4):543–550.]</p

Nearby early-type galaxies with ionized gas. III. Analysis of line-strength indices with new stellar population models

In this paper we study the underlying stellar population of a sample of 65 nearby early-type galaxies predominantly located in low density environments. Ages, metallicities and [alpha/Fe] ratios have been derived through the comparison of Lick indices measured at different galacto-centric distances with new SSP models which account for the presence of alpha/Fe enhancement. The SSPs cover a wide range of ages, metallicities and [alpha/Fe] ratios. To derive the stellar population parameters we have devised an algorithm based on the probability density function. We derive a large spread in age ((1-15) Gyrs). Age does not show any significant trend with central velocity dispersion sigma_c but E galaxies appear on average older than S0. On the contrary, an increasing trend of metallicity and [alpha/Fe] with sigma_c is observed, testifying that the chemical enrichment was more efficient and the duration of the star formation shorter in more massive galaxies. We have also sought for possible correlations with the local galaxy density but neither metallicity nor alpha-enhancement show clear trends. However we find that while low density environments (LDE) contain very young objects (from 1 to 4 Gyr), none of the galaxies in the higher density environments (HDE) is younger than 5 Gyrs. Considering the lack of environmental effect on the [alpha/Fe] ratio and the high value of [alpha/Fe] in some young massive objects, we argue that young galaxies in LDE are more likely due to recent rejuvenation episodes. By comparing the number of rejuvenated objects with the total number of galaxies in our sample, and by means of simple two-SSP component models, we estimate that, on average, the rejuvenation episodes do not involve more than 25 % of the total galaxy mass.Comment: Final version as it will appear in A&A. Typos in the Abstract and Conclusions have been correcte

Nature vs. nurture in the low-density environment: structure and evolution of early-type dwarf galaxies in poor groups

We present the stellar population properties of 13 dwarf galaxies residing in poor groups (low-density environment, LDE) observed with VIMOS@VLT. Ages, metallicities, and [alpha/Fe] ratios were derived from the Lick indices Hbeta, Mgb, Fe5270 and Fe5335 through comparison with our simple stellar population (SSP) models accounting for variable [alpha/Fe] ratios. For a fiducial subsample of 10 early-type dwarfs we derive median values and scatters around the medians of 5.7 \pm 4.4 Gyr, -0.26 \pm 0.28, and -0.04 \pm 0.33 for age, log Z/Zsun, and [alpha/Fe], respectively. For a selection of bright early-type galaxies (ETGs) from the Annibali et al.2007 sample residing in comparable environment we derive median values of 9.8 \pm 4.1 Gyr, 0.06 \pm 0.16, and 0.18 \pm 0.13 for the same stellar population parameters. It follows that dwarfs are on average younger, less metal rich, and less enhanced in the alpha-elements than giants, in agreement with the extrapolation to the low mass regime of the scaling relations derived for giant ETGs. From the total (dwarf + giant) sample we derive that age \propto sigma^{0.39 \pm 0.22}, Z \propto sigma^{0.80 \pm 0.16}, and alpha/Fe \propto sigma^{0.42 \pm 0.22}. We also find correlations with morphology, in the sense that the metallicity and the [alpha/Fe] ratio increase with the Sersic index n or with the bulge-to-total light fraction B/T. The presence of a strong morphology-[alpha/Fe] relation appears to be in contradiction to the possible evolution along the Hubble sequence from low B/T (low n) to high B/T (high n) galaxies. We also investigate the role played by environment comparing the properties of our LDE dwarfs with those of Coma red passive dwarfs from the literature. We find possible evidence that LDE dwarfs experienced more prolonged star formations than Coma dwarfs, however larger data samples are needed to draw more firm conclusions.Comment: Accepted for publication on A&

The SAURON project. II. Sample and early results

Early results are reported from the SAURON survey of the kinematics and stellar populations of a representative sample of nearby E, S0 and Sa galaxies. The survey is aimed at determining the intrinsic shape of the galaxies, their orbital structure, the mass-to-light ratio as a function of radius, the age and metallicity of the stellar populations, and the frequency of kinematically decoupled cores and nuclear black holes. The construction of the representative sample is described, and its properties are illustrated. A comparison with long-slit spectroscopic data establishes that the SAURON measurements are comparable to, or better than, the highest-quality determinations. Comparisons are presented for NGC 3384 and NGC 4365 where stellar velocities and velocity dispersions are determined to a precision of 6 km/s, and the h3 and h4 parameters of the line-of-sight velocity distribution to a precision of better than 0.02. Extraction of accurate gas emission-line intensities, velocities and line widths from the datacubes is illustrated for NGC 5813. Comparisons with published line-strengths for NGC 3384 and NGC 5813 reveal uncertainties of < 0.1 A on the measurements of the Hbeta, Mgb and Fe5270 indices. Integral-field mapping uniquely connects measurements of the kinematics and stellar populations to the galaxy morphology. The maps presented here illustrate the rich stellar kinematics, gaseous kinematics, and line-strength distributions of early-type galaxies. The results include the discovery of a thin, edge-on, disk in NGC 3623, confirm the axisymmetric shape of the central region of M32, illustrate the LINER nucleus and surrounding counter-rotating star-forming ring in NGC 7742, and suggest a uniform stellar population in the decoupled core galaxy NGC 5813.Comment: 20 pages, 17 figures. To be published in MNRAS. Version with full resolution images available at http://www.strw.leidenuniv.nl/~dynamics/Instruments/Sauron/pub_list.htm

RhoA Regulates Peroxisome Association to Microtubules and the Actin Cytoskeleton

Peer reviewe