18512375
GALEX UV properties of the polar ring galaxy MCG-05-07-001 and the shell galaxies NGC 1210 and NGC 5329
Context. Systems of shells and polar rings in early-type galaxies are considered “bona fide” tracers of mass accretion and/or mergers. Their high frequency in low density environments suggests that these processes could drive the evolution of at least a fraction of the early-type galaxy population. Aims. We investigate the star formation histories of this type of galaxies. Their UV emission is important for testing whether these galaxies host ongoing or recent star formation and how this formation varies across the galaxy. Methods. We used far- and near- ultraviolet, optical, near-infrared images, neutral hydrogen HI maps, and line-strength indices to investigate the nuclear and outer regions of these galaxies as well as the regions where fine structures are present. Results. The GALEX near UV (NUV) and far UV (FUV) images of MCG-05-07-001 and NGC 1210 show complex tidal tails and debris structures. The far UV morphology of both galaxies appears so different from the optical morphology that the early-type classification may not apply. In both GALEX bands, the polar ring of MCG-05-07-001 is the dominant feature, whereas an extended tidal tail dominates the FUV bands of NGC 1210. In MCG-05-07-001 and NGC 1210, there is a strong correlation between structures detected in the FUV and NUV bands and in HI. In contrast, NGC 5329 does not show evidence of shells in the GALEX bands. We try to constrain the age of the accretion episode or merger that produced the shells and polar rings with the aid of composite stellar populations that take the presence of dust into account. The presence of HI in both MCG-05-07-001 and NGC 1210 argues in favour of wet mergers. Models suggest the presence of very young stellar populations in MCG-05-07-001: the observations could be explained in the framework of a conspicuous burst of star formation that occurred ≤1 Gyr ago and involved a large fraction of the galaxy mass. Our models suggest that also the nuclei of NGC 1210 and NGC 5329 could have been rejuvenated by an accretion episode about 2–4 Gyr ago.
16975153
The bright galaxy population of five medium redshift clusters II. Quantitative galaxy morphology
Aims. Following the study presented in our previous paper, based on the Nordic Optical Telescope (NOT) sample, which consists of five clusters of galaxies within the redshift range 0.18 ≤ z ≤ 0.25 imaged in the central 0.5–2 Mpc in very good seeing conditions, we have studied the quantitative morphology of their bright galaxy population Methods. We analyzed the surface brightness profiles of the galaxy population in those clusters, after performing simulations in order to check the reliability of the fits. We also derived a quantitative morphological classification. Results. The structural parameters derived from these analyses are presented. We obtained that the structural parameters of E/S0 galaxies are similar to those shown by galaxies in low redshift clusters. However, the disc scales are different. In particular, the scales of the discs of galaxies in medium redshift clusters are statistically different than those located in similar galaxies in the Coma cluster. However, the scales of the discs of galaxies in medium redshift clusters are similar to nearby field galaxies. Conclusions. Our results suggest that the evolution of the disc component of galaxies in clusters is faster than in field ones. Mechanisms like galaxy harassment showing timescales of ∼1 Gyr could be responsible for this disc scale evolution. This indicates that spiral galaxies in clusters have undergone a strong evolution in the last 2.5 Gyr or that Coma is in some way anomalous.
14891588
The visible environment of galaxies with counterrotation
In this paper we present a statistical study of the environments of 49 galaxies in which there is gas- or stellar-counterrotation. The number of possible companions in the field (to apparent magnitude 22), their size and concentration were considered. All the statistical parameters were analysed by means of Kolgomorov-Smirnov tests, using a control sample of 43 galaxies without counterrotation. From our data, no significant differences between the counter-rotating and control samples appear. This is different to Seyfert or radio-loud galaxies which lie in environments with a higher density of companions. On the contrary, if a weak tendency exists, for galaxies with gas counterrotation only, it is discovered in regions of space where the large scale density of galaxies is smaller. Our results tend to disprove the hypothesis that counterrotation and polar rings derive from a recent interaction with a small satellite or a galaxy of similar size. To a first approximation, they seem to follow the idea that all galaxies are born through a merger process of smaller objects occurring very early in their life, or that they derive from a continuous, non-traumatic infall of gas that formed stars later. Whatever the special machinery is which produces counterrotation or polar rings instead of a co-planar, co-rotating distribution of gas and stars, it seems not to be connected to the present galaxy density of their environments.
119325667
The scaling relations of early{type galaxies in clusters ? I. Surface photometry in seven nearby clusters
This is the first paper of a series investigating the scaling relations of early–type galaxies in clusters. Here we illustrate the multi–band imagery and the image reduction and calibration procedures relative to the whole sample of 22 clusters at $0.05 \mathrel{\raise0.35ex\hbox{$\scriptstyle <$}\kern-0.6em \lower0.40ex\hbox{{$\scriptstyle \sim$}}}z \mathrel{\raise0.35ex\hbox{$\scriptstyle <$}\kern-0.6em \lower0.40ex\hbox{{$\scriptstyle \sim$}}}0.25$. We also present detailed surface photometry of 312 early–type galaxies in 7 clusters in the first redshift bin, $z \approx0.025$–0.075. We give for each galaxy the complete set of luminosity and geometrical profiles, and a number of global, photometric and morphological parameters. They have been evaluated taking into account the effects of seeing. Internal consistency checks and comparisons with data in the literature confirm the quality of our analysis. These data, together with the spectroscopic ones presented in the second paper of the series, will provide the local calibration of the scaling relations.
18425047
The peculiar galaxy IC 1182: An ongoing merger?
Broad and narrow band images and long slit spectroscopy of IC1182 are presented. The broad band images reveal a distorted morphology with a large, heavily obscured disk-like structure and several knots in the central region. Galactic material, some of it in the form of two tails, is detected well beyond the main body of the galaxy. The second, fainter tail and several knots are reported here for the first time. The narrow band images show that the galaxy is a powerful emitter. The emission in the main lines extends all over the galaxy, with plumes and arc-like structures seen in H$\alpha$ at large distances from the center. The uncorrected H$\alpha$ flux corresponds to 3.51$\times10^{41}$ erg s$^{-1}$, 3 times that of Arp 220. The internal extinction deduced from the Balmer decrement is high all along the slit, with E$_{B-V}\approx$ 1. There are no clear signs of nuclear activity and the observed line ratios can be explained in terms of stellar photoionization. The metallicity of the gas in the two brightest central knots is low, 0.1 Z$_{\odot}$ and 0.06 Z$_{\odot}$ respectively. In the main body of the galaxy, besides the reported knots, the distribution of the ionized gas resembles that of an inclined disk about 12 kpc in size. The rotation pattern is complex and corresponds to two identifiable disk galaxies with observed rotation amplitudes of 200 \kms and 100 \kms respectively. The data presented here indicate that IC 1182 is a high luminosity starburst system, involving two systems in the process of merging, with two tidal tails emerging from the central region of the galaxy.
1840
Cluster formation in the LMC
In this work we present preliminary results concerning the properties of about 50 clusters and associations located in a densely populated region at the Southern edge of the supershell LMC~4. The ages of the clusters and associations are derived. The cluster formation rate peaks at about 10-20 Myr ago corresponding to the age of the formation of LMC~4. Objects younger than 10 Myr are located close to CO clouds, indicating a possible trigger of the recent star formation by the interaction of the supershell with the interstellar medium. 
Isophotal analysis has been done for 50% of the clusters. A large number of objects present isophotal distortions commonly interpreted as sign of interaction. Cluster multiplets are coeval within 20 Myr, suggesting a common origin. This indicates that clusters possibly form in large groups. Our findings are in agreement with the unified view of multi-scale star formation, where a size-duration correlation is expected.
85534134
Extended LCDM: generalized non-minimal coupling for dark matter fluids
In this paper we discuss a class of models that address the issue of explaining the gravitational dynamics at the galactic scale starting from a geometric point of view. Instead of claiming the existence of some hidden coupling between dark matter and baryons, or abandoning the existence of dark matter itself, we consider the possibility that dark matter and gravity have some non trivial interaction able to modify the dynamics at astrophysical scales. This interaction is implemented assuming that dark matter gets non-minimally coupled with gravity at suitably small scales and late times. After showing the predictions of the model in the Newtonian limit we also discuss the possible origin of it non-minimal coupling. This investigation seems to suggest that phenomenological mechanisms envisaged for the dark matter dynamics, such as the Bose-Einstein condensation of dark matter halos, could be connected to this class of models.
123275132
The new scintillating fiber detector of E835 at Fermilab
Abstract The scintillating fiber tracker for the measurement of the polar coordinate θ for experiment E835 at Fermilab has been upgraded, by adding two extra layers (240 fibers each), at R ≈9 cm from the beam axis. Photons from the fibers are detected by Visible Light Photon Counters (VLPCs). The high granularity, flexibility and fast response of the scintillating fibers, combined with the high quantum efficiency of the VLPCs, allow high rate capability, high efficiency, good tracking and time resolution. Signals from the outer two layers are used to provide θ information to the first-level trigger.
118311491
Dark matter as a Bose-Einstein Condensate: the relativistic non-minimally coupled case
Bose-Einstein Condensates have been recently proposed as dark matter candidates. In order to characterize the phenomenology associated to such models, we extend previous investigations by studying the general case of a relativistic BEC on a curved background including a non-minimal coupling to curvature. In particular, we discuss the possibility of a two phase cosmological evolution: a cold dark matter-like phase at the large scales/early times and a condensed phase inside dark matter halos. During the first phase dark matter is described by a minimally coupled weakly self-interacting scalar field, while in the second one dark matter condensates and, we shall argue, develops as a consequence the non-minimal coupling. Finally, we discuss how such non-minimal coupling could provide a new mechanism to address cold dark matter paradigm issues at galactic scales.
118368961
Non-minimally coupled dark matter: effective pressure and structure formation
We propose a phenomenological model in which a non-minimal coupling between gravity and dark matter is present in order to address some of the apparent small scales issues of ΛCDM model. When described in a frame in which gravity dynamics is given by the standard Einstein-Hilbert action, the non-minimal coupling translates into an effective pressure for the dark matter component. We consider some phenomenological examples and describe both background and linear perturbations. We show that the presence of an effective pressure may lead these scenarios to differ from ΛCDM at the scales where the non-minimal coupling (and therefore the pressure) is active. In particular two effects are present: a pressure term for the dark matter component that is able to reduce the growth of structures at galactic scales, possibly reconciling simulations and observations; an effective interaction term between dark matter and baryons that could explain observed correlations between the two components of the cosmic fluid within Tully-Fisher analysis.
110897779
The E835 scintillating fiber tracking detector
This paper describes the scintillating fiber tracking detector designed and built for the Fermilab experiment E835. This detector uses Visible Light Photon Counters (VLPC) readout system and is in use at the p ¯ accumulator ring at Fermilab. A description of the components of the detector and preliminary results of its performances are given.